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  1. #1

    Technical info about 8.8 conversions

    First thing I want to do is recognize the following people & locations this info was compiled from: CODE 4X4, Wally,,,

    CODE 4X4

    Ford 8.8 specs:

    Weight (complete assembly w/ brakes etc.): 174 lb.

    Drivers side Ford brake hose #: F5TZ-2282-A

    Passenger side brake hose #: XL2Z-2282-AA

    Banjo bolt (caliper) Ford #: 385116 S 2

    Bolt size (U-joint flange to yoke) is: 12 x 1.75 x 30 mm

    The axle shaft strength (tested by Warn Ind.) is as follows:

    F8.8= 6,500 (lb. ft.)

    D44= 4,600-5,000 (lb. ft.)

    D35C= 4,000-4,300 (lb. ft.)

    Sorry, I do not have D60 or F9" shaft strength.


    O.D. of tubes: 3.250".

    Tube thickness: .250" (some are .188"!)

    Ring gear diameter: 8.800".

    Ring gear bolts: 7/16" dia. (qty. 10).

    Pinion diameter/splines: 1.625 / 30.

    Axle shaft/splines: 1.320 / 31.

    Rotor thickness (where it mounts to axle is .250").

    Overall width* 59.625" (the F8.8 is .950" narrower then a TJ Dana 35).

    Hole diameter for ABS sensor in top of housing: .811".

    Centerline of housing to C/L of pinion difference is 3.875" toward the P/S.

    Pinion offset: P/S to C/L of Pinion, 27-3/4" (no rotor on axle), D/S to C/L of Pinion, 31-5/8" (no rotor on axle). (this measurement is 2.5" more offset to the P/S then a TJ Dana 35).

    *Explorer & Mountaineer. The F-150 8.8 is drum brake and width WMS to WMS is 65.5".


    Code Capacity Ratio
    43 Open 3200 3.08
    41 Open 3200 3.27
    42 Open 4.10
    46 Open 3.73
    45 Open 3200 3.55
    D4 Limited Slip 3200 3.73
    D2 Limited Slip 4.10
    L73 Limited Slip 3.73
    L - Limited Slip Differential
    C - Conventional Differential
    Code Ratio
    41 3.27
    43 3.08
    42 3.45
    44 3.73
    45 3.55
    47 4.10
    72 3.08C
    74 3.45C
    82 3.08C
    84 3.45C
    85 3.55C
    86 3.73C
    87 4.10C
    89 (1992-1998) 4.10C
    89 (1999-2001) 4.56C
    91 3.27C
    92 3.08C
    95 3.55C
    96 3.73C
    97 4.10C
    F4 3.45L
    F5 3.55L
    F6 3.73L
    F7 4.10L
    K6 4.10L
    D2 3.45
    D4 3.73L
    D7 4.10
    R5 3.55L
    R6 3.73L
    R7 4.10L

    Some of the ones on the second list do not apply to the Explorer 8.8 (like the 4.56 one) as this list covers rangers too.


    Item........................Part Supplier..............Actual $........Est $

    1/2" Ubolt Plates...............Bonner Steel.............$36.00......$35.00
    Ubolts.............................Alcan Spring.............$25.84......$28.50
    Driveshaft Flange..............Drivetrain Industries...$18.99......$25.00
    4 Bolts for Drive Flange......Ford Dealer...............$7.92........$6.00
    Spring Perches.................Jeep Dealer...............$11.10.......$14.35
    Pass Soft Brake Line..........Autozone.................$24.75.......$25.00
    Caliper Pads.....................Autozone.................$32.64.......$35.00
    Turn Rotors......................Checkers.................$15.00.......$15.00
    Brake Fluid.......................Autozone.................$3.32.........$3.50
    Steel Brake Lines..............Autozone..................$6.15........$6.00
    Gear Oil...........................Autozone..................$7.27........$8.00
    2 Cans of Black Paint.........Autozone..................$10.84.......$10.84
    Shock Mounts..................Mountain Offrosd........$25.65.......$30.00
    MORE Ebrake Cables..........Mountain Offrosd........$126.38.....$115.00

    Most Rangers are equipped with the Ford 7.5-inch rear axle with several exceptions:

    1) 1986-up "Incomplete vehicles" also known as "Chassis Cabs" were frequently equipped with 8.8" 28-spline axles, the '86-88 examples are distinctive as they are the only 8.8" Ranger rears that have no provisions for a RABS sensor.

    2) 1990 & up 4.0-liter Rangers. These are ALWAYS equipped with the 8.8-inch 28-spline rear axle.

    3) 1998-up 4x4 supercab Rangers regardless of powerplant are frequently equipped with 8.8" axles

    4) FX4 Rangers 99-current come equipped with an 8.8 rear and 31-spline axles with either 4.10 or 4.56 axle ratios.

    Swapping in an 8.8-inch 28-spline Ranger axle for the original 7.5-inch axle provides (according to Ford) a 35% increase in strength. But this strength increase refers to the greater strength of the gears and carrier bearings (Pinion bearings, axle bearings and axle shafts are exactly the same) there is NO increase in weight capacity If you are looking for greater strength for loads created by severe offroad driving or towing you'll want to go to the next step, the Explorer axle.

    The rear axles on all Ford Explorers are also 8.8's, however there are some differences... The 8.8-inch Explorer axle use 31-spline axle shaft. Increasing from a 28-spline to a 31-spline axle allegedly increases strength of the axle shaft by 34%, however I'll go by the capacity ratings of the axle assemblies provided by the manufacturer. Ford Rates the Ranger axle at 2750lbs and the Explorer axle at 3200lbs this is a 16% increase in strength, which admittedly may be as conservative
    as the estimate of axle strength. The Important thing about the Explorer axle assembly vis-a-vie it's strength is not the axles that are larger at the splines but that these axles are larger in diameter at the outer bearing journal AND the larger diameter bearings used.

    What axle do you have now?

    You can identify which axle you have by the tag attached to the inspection cover.

    Some feel better having disc brakes (I'll discuss this elsewhere and if you want discs then look for a Explorer '95-01, as these are the ones with the disks brakes. '91-94 axle assemblies are just as strong, but have 10" drums (Which are more easily connected to your existing hydraulic lines and Parking brake cables)

    7.5-inch Rear Specifications

    7.5-Inch Ring Gear

    1.626" Pinion Stem

    8.8-inch Rear Specifications

    8.8-Inch Ring Gear

    1.626" Pinion Stem

    Swapping a Ranger 7.5-inch to a Ranger 8.8-inch is a direct replacement. Swapping in a stronger 8.8-inch from an Explorer requires mounting the spring perches from under to over the axle. This should be done by a reputable welder. The '95 & newer Explorer 8.8-inch axles have disk brakes. The master cylinders in the Rangers are not calibrated for rear disk brakes. When converting to rear disks you should replace your master cylinder with one from a rear disk brake Explorer.

    Axle Width Differences:

    People have asked about the widths of axle shafts to swap shafts from one axle to another.

    The early 1983-1992 Ranger axles are 1" shorter than the 1993-up pieces. (Both sides) meaning that the an entire Ranger axle assembly from 1993-up is 2-inches wider than 1983-1992.

    The right side Bronco II axle shaft is 1-5/8" wider than the 1983-1992 Ranger shaft. All of this additional width is in the passenger side. The drivers side shaft is the same length in either axle assembly.

    On ALL Ranger/bronco II's the drivers side axle shaft is longer than the passenger side.

    There is no difference between 7.5 & 8.8 axle shaft lengths provided you stay in the same year window.

    As a note, if you go to a salvage yard, you'll find many left-side shafts removed from 1983-1992 Rangers and Bronco II's. These axle shafts are the same length as the axle shafts in the "Fox" (1979-1993) Mustangs EXCEPT that Ranger/bronco II shafts are five-lug and Mustangs are four lug. Ranger/Bronco II shafts are frequently "pillaged" for use in converting a Mustang to five-lug wheels.


    The 7.5-inch and 8.8-inch axles retain the axles using C-Clips. A broken C-Clip axle will slide out of the axle tube. C-Clip eliminators are available which hold the axle in the axle tube.

    Ford Part# M-4220-A

    Jegs Part# 873-A1092

    Axle Girdle:

    Serious Off-Roaders should consider installing an Axle Girdle. They Replace the existing inspection cover and provide support to the differential bearing caps. They also increase the fluid capacity.

    Ford Part# M-4033-G (8.8-inch)

    Ford Part# M-4033-J (7.5-inch)

    Jegs Part# 6-9-101-8.8 (8.8-inch)

    A trucks off-road performance can be greatly enhanced using a locker. There are different ways that you can lock the rear end.

    (1) An air locker (Expensive) solidly locks the rear end together using a small air-compressor attached to a locker in the differential.

    (2) A spool (Not Recommended) solidly locks the rear axles but should only be used for off-road competition since it doesn't let the axles turn at different speeds while cornering.

    (3) A Lincoln Locker (Same as spool) is simply welding the spider gears in the differential together.

    (4) A Detroit locker replaces the whole carrier and unlocks when turning.

    (5) A Lock-Right is the most popular because it replaces the existing spider gears, unlocks while turning, is affordable, and doesn't require setting up the ring and pinion like a Detroit Locker would.

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  2. #2

    Technical info about 8.8 conversions Page-2

    Axle Truss:

    An Axle Truss should be considered to protect your Axle from bending during serious off-road use, particularly if you like doing something silly like "Jumping" your truck. Desert racers in particular should have one of these because getting airborn is "normal use" for them. For most people the additional strength added by a truss is cheap insurance against damaging an expensive axle A slight bend in an axle tube will quickly wear out the axles shafts and bearings may damage the differential itself as well as cause distinctive wear to your expensive offroad tires. And of course serious bending of the housing can cause the axle to break the axle leaving you stuck and in possession of a hefty towing bill.

    The only downside to an axle truss is that it will reduce clearance between the ground and the axle, but the clearance reduction is well worth the protection from bending an expensive axle assembly.

    The only commercially made axle truss for Rangers and Bronco2's that I am aware of is made by James Duff and can be seen in their online catalog.

    Gear Ratios:

    If your considering a change in your gear ratio you should use the 'Off-Road Calculators' on the main page of this website.


    Ford began using the 8.8" axle in Rangers circa 1986 on "incomplete vehicles" aka "chassis cabs" (as mentioned above), but the 8.8" axles only became common in Rangers with the introduction of the 4.0L V6 in mid-1990. It began appearing in Explorers (and Mazda's Navajo twin) in 1991. It has also been used in 4.0L Aerostars (2wd ONLY, the 4.0 AWD Aerostars, strangely, are equipped with the 7.5" axle), From mid'84-up F-150 (Except for 5.4liter "Lightning's and Some 4x4 Supercabs which are equipped with the heavier-duty 9.75" rear axle) '84-1/2 on Full-size Broncos, and E-150 Econoline vans.

    The 8.8 is also used in other Ford products such as Mustangs, Thunderbirds ("solid axle" '87-88 with 2.3 turbo engine and 5.0 "Sport" models), Crown Victorias and their equivalent Mercury and Lincoln products. However, because of their different suspensions, they make undesirable choices for swapping into a Ranger (unless you're looking to also swap to a four-link rear suspension for airbags and such).

    An IRS version also appeared in the '89-97 Thunderbird, Mercury Cougar, (Though there is also a 7.5" IRS in some V6 cars), the Lincoln Mark VIII and finally a very similar IRS suspension was adapted for the Mustang Cobra.

    A wide range of gear ratios is available, from 3.08's up to 5.13's. An equally wide array of differentials is also available from open carriers to limited slips to lockers and spools.

    8.8" axles can have either 28-spline or 31-spline axles.

    All car applications use 28-spline axles, all truck applications use 31-spline axle shafts EXCEPT Rangers, which use 28-spline axles, however even Exceptions have Exceptions, FX4 Rangers 99-current with 4.10 or 4.56 axle ratios are built with 31-spline axles.

    Gear sets are interchangeable between axles, regardless of the spline count. Differentials, however, are not.

    Here is a guide for the purchase and build-up of the Ford 8.8 rear axle and its compatability and performance in a Wrangler or Cherokee.
    I did a little scrounging around on Jeeps Unlimited and came up with some questions asked and answers given along with some of our experiences. Below there are many links to build-ups and all kinds of info.
    There are many different variations of the Ford 8.8 axle. One of them is best suited for the use in a Jeep and that would be the Explorer (or Mountaineer) 31 spline 8.8. If you have found one off a Aerostar, Mustang, F-150 etc, you should really pass it up and look for a Explorer axle if you wish to retain a similar track width on your Wrangler. Trying to start your build-up with the wrong axle will be frustrating and expensive although you may have picked it up for cheap in the beginning.

    Ford 8.8 assembly specs:
    Cover bolt 28-38 ft.lbs.
    Pinion bearing preload 16-29 in.lbs.
    Pinion bearing preload 8-14 in.lbs (used)
    Ring gear backlash .008-.015
    Ring gear bolt to case 70-85 ft.lbs
    Side bearing caps 70-85 ft.lbs.

    Explorer 8.8 Measurements:
    Weight (complete assembly w/ brakes etc.): 174 lb.
    O.D. of tubes: 3.250".
    Tube thickness: .250" (some are .188”!)
    Ring gear diameter: 8.800".
    Ring gear bolts: 7/16" dia. (qty. 10).
    Pinion diameter/splines: 1.625 / 30.
    Axle shaft/splines: 1.320 / 31.
    Rotor thickness (where it mounts to axle is .250").
    Overall width 59.625" (the F8.8 is .950" narrower then a TJ Dana 35).
    (The F-150 8.8 is drum brake and width WMS to WMS is 65.5”.)
    Hole diameter for ABS sensor in top of housing: .811".
    Bolt size (U-joint flange to yoke) is: 12 x 1.75 x 30 mm
    Centerline of housing to C/L of pinion difference is 3.875" toward the P/S.
    Pinion offset: P/S to C/L of Pinion, 27-3/4" (no rotor on axle), D/S to C/L of Pinion, 31-5/8" (no rotor on axle). (this measurement is 2.5" more offset to the P/S then a TJ Dana 35).

    How many splines are the axle shafts?
    drivers side is 31 spline for 97 & up Mountaineer, 95 & up Explorer, 30-1/2 inch length - 5 X 4.5 inch lug pattern.
    passenger side is 31 spline for 97 & up Mountaineer, 95 & up Explorer, 27-5/8 inch length - 5 X 4.5 inch lug pattern

    Can I get 35 spline shafts?
    Yes, with a little searching I found 28 and 33 splines too. Remeber 8.8 axles are used on many different Ford rigs. Mustangs, Rangers, F150s, Aerostar etc... different axle lengths than the Explorer so if you are looking for aftermarket products make sure you are not looking at something for a Mustang that might not fit an Explorer. For the 35 spline stuff check with Mark Williams site. i dont have a link yet but i will soon.

    Do I need a slip yoke eliminator?
    In my opinion, yes

    Can I use my drive shaft that I bought for my SYE/Dana 35 set-up?

    Is the 8.8 narrower than a Dana 35?
    Yes but not enough to make a difference when running most aftermarket wheels.1.5" shorter or so. It doesn't matter unless you try running stock rims w/12.5 or wider tires.

    Are the 8.8 shafts stronger than Dana 44 shafts?
    Yes, also the bearings, pinion and ring gear are also much larger.

    Axle shaft Strength and output torque rating by 4 Wheeler
    (Numbers from January edition of Fourwheeler, page 60.)
    Dana 35 rear axle COT: 870 MOT: 3480
    Dana 44 rear axle COT: 1100 MOT: 4460
    Ford 8.8 28spline COT: 1250 MOT: 4600
    Ford 8.8 31spline COT: 1360 MOT: 5100
    Dana60 semifloat COT: 1500 MOT: 5500]

    Will I need that brake proportioning valve from a Rubicon?
    Probably not

    Does the 8.8 offer more ground clearance over the Dana 35 and 44?
    Not under the differential but the bigger axle tubes lift the rig about 5/8 ".

    Is there welding involved?
    Yes, but the new brackets you put on are much stronger than stock Dana’s. Not a good idea to re use your old Dana 35 brackets

    Where do I get brackets?
    4x4 Group Buy has Rubicon Express for.
    Bob Supplee has Tera.
    DC4WD has Tera.
    Carolina Rock Shop (call or email for price quote)
    TeraFlex TMI-ABK-TR
    M.O.R.E. Dana 35 bracket (sku:MORE98700)
    Rubicon Express RE9969 TJ Axle Bracket Kit Rear
    MAD 4WD

    The list above should get you headed in the right direction as far as brackets go. Look around and compare prices as the brackets can be found for $200.00 or less shipped sometimes. Keep this in mind when shopping for any item for your build-up,if you do, you will save a bundle.

    Can I reuse my Dana 35 brackets?
    Yes, but it is not recomended. The stock Dana 35 brackets are sort of flimsy compared to the beefy aftermarket versions. Some of the brackets available are in fact for Dana 35 axles to replace the weak ones that come factory. Reusing the D-35 brackets is time consuming even if you have the right tools, not a good idea IMO

    Should I weld the axle tubes to the cast housing?
    I would if it had been salvaged from a wrecked rig. If it is new on a crate (in my opinion) don’t bother.

    Will my stock sway bar work?
    Yes, with a minor modification to a passenger side pinion gusset.

    Do all 8.8s come with a limited slip?
    No, read the tag on the housing or remove the cover. 3L73 = 3.73 gears witha "L"imited slip

    Where is the gear break for lockers?
    There is no break. Same locker for 3.73 to 6.14
    Do I need a notched cross pin? Yes for 4.56-6.14 to clear ring gear, or notch a gear tooth.

    More cross pin info from NovaTJ:
    The 3/4 inch cross pin only fits those rears with the 28 spline count period!
    Therefore, the 7/8 inch crosspin is what we are concerned with and it fits Explorer, Mountaineer, F150, and Expedition's with the 8.8 ring gear and 31 spline axles. It also come in those special Mustangs that have the 31 spline axles i.e. Cobra, Steeda, and Rousch.

    The axles for Jeep conversion we are keen on are the 96 through 2001 Ford Explorer and Mercury Mountaineer with disc brakes and all that fall into this category with or without limited slip have the 7/8 inch cross pin.


  3. #3

    Technical info about 8.8 conversions Page-3

    Convert from a 28 to a 31 spline??? Need bigger axle tubes too! The bearing on a 31 spline is much bigger than a 28 spline bearing.

    What year ford explorers do I look for as a donor for 31 spline and disc brakes? To get rear disc brakes and 31-spline axle, you need to look for a 1995 to 2001 Explorer or Mountaineer. Earlier years use drum brakes and may be 28-spline. Different vehicles may have the wrong bolt pattern, width, spline count, or brakes. A 2-door Sport Explorer may be a donor past the 2001 cut off. Also, Explorer SportTracs with production dates of August 19, 2002 through June 29, 2005 are equipped with 31-spline axles and rear disc brakes and are exactly what was in the previously listed 95-2001 Explorer. Before Aug 19, 2002, the Sport Tracs were equipped with the smaller 28-spline 8.8 axle shafts and used drum brakes. After June 29, 2005, Sport Tracs were produced with an Independent rear as found on 2002 regular Explorers.* Sport-Trac donor info from NovaTJ

    What is so great about 8.8?
    Parts are everywhere, as in axle shafts, covers, brake parts etc..

    What's not so great about the 8.8?
    Weak stock carrier, replace with a carrier type locker like ARB or Detroit (not a lunch box type) this will cure the problem.

    Spun axle tubes: Simply weld the tubes into the diff housing before they spin. You are welding to cast steel so now would be the time to ask for a professional's opinion. I have heard of guys tossing the works in a oven before welding, some just go at it cold. Both say their way is right.

    Thin stock diff cover: Get some armor.

    (my axle was new surplus and had not been in a collision, i know exactly where it has been from mile one and it is not welded. I dont believe my wheeling style will cause me problems, however i do keep a close eye on the plug welds.)

    What kind of locker can I get?

    What is the bolt pattern?
    5 on 4.5” just like stock TJ/YJ wheels.

    Will my Jeep lug nuts fit the 8.8?
    In most cases, yes.

    What do I do with the speed sensor?
    leave it in place.

    Where to buy?
    wallysheata, Ariel Performance
    to name a few.

    How much do they cost?
    Free to $1500.00 but you can find them new for around $500.00 in their stock form complete disc to disc.

    What do I need for a swap into a TJ?
    Here are some things I used:

    -TeraFlex Bracket kit
    -U.S. Gears 4.56
    -Master install kit (Timken)
    -Crane diff cover
    -Napa brake line kit P/N 380528 (x2)
    -T-hose NAPA P/N 380889
    -ZJ E-brake cables (drivers and passenger side)
    Mopar P/N 52008904 & 52008905
    NAPA P/N 95342 (right) 95347 (left). (not for YJs)
    -Driveshaft adapter: Spicer 2-2-1379
    -Flange bolts Ford P/N N800594-S100 (x4)
    -'03 TJ Rubicon (w/disc) proportioning valve P/N 5083808AA
    -3/16" hard brake line about 40" & 18"

    HELPFUL SITES be sure to check these out:
    Dome & Detour
    8.8 Swap
    J.E. Towle / DPG Offroad
    Chris Overacker / CODE 4x4
    4x4 Wire Links
    The Ranger Station Tech Library
    The Ranger Station Tech Library 2

    YJ & XJ STUFF:

    From M.O.R.E.
    -XJ Installation Kit P/N 98600 84-2001 XJ
    -XJ E-Brake Cable Kit P/N EB3 Disc Brake F8.8 Only
    -Special Yoke P/N 221379 F8.8 to 1310 U-Joint

    From Dealership:
    -Mopar spring perches
    -Tabs for shock mounts
    -ZJ ebrake cables from the dealer (for XJ install)
    -Flange from spicer dealer $30 (have seen this go from $20-$50)


    Stock brake cables won't come off bracket at tub. Pound a deep 13mm socket on the cable end to compress the fingers holding it in place.

    Add gear oil through the abs sensor hole at the top. With an 19 degree pinion angle, I just pour three quarts in and call it full.

    To replace axle seals, use the end of the removed axle shaft to pry the seal out.

    Axle shaft bearings...remove the seal first as above, then slide hammer the bearings out.

    Parking brake shoes can make rotor removal a pain after rust sets in, I always machine the inside lip of the rotor (drum section) about 3/8 inch from the edge to the edge about .030 deep so rust won't interfere by dragging on the shoes.

    Old parking brake shoes can have the lining come loose from the metal part of the shoe...reglue with two part epoxy if new shoes not readily available...(it's only a parking brake).
    Parking brake shoes from Ford...$115 set! Autozone...about $20!
    BENT SHAFT????

    Ford Explorer 8.8" Axle Install in a '95 Jeep Wrangler

    Why I Did It

    In June of 2002, I got tired of having no traction in my YJ's stock axles, so I installed a used (but quite good) Trac-Lok limited slip in my rear Dana 35. The added boost in traction was great. I quickly realized that if you apply light break pressure, the Trac-Lok became almost as good as a real locker. Of course, you need more throttle to compensate for the brake drag. This lead to a more aggressive driving style when climbing hills and ledges. Unfortunately, aggressive driving, 33" tires, and a D35 axle don't go well together.

    After this trip in September 2003, I noticed something was wrong with my rear axle. I first thought it was just another stretched pinion yoke, the product of too much axle wrap without a ladder bar. I'd already replaced one rear yoke in December 2002 (the '94-95, 1330-style yoke is Spicer P/N 2-4-7631-1, BTW), so I was familiar with the symptoms and procedure. When I went to replace the yoke, I heard some mild grinding noises from inside the axle when I'd rotate the pinion. Unfortunately, further diagnosis indicated that the rosette welds that hold my passenger side axle tube into the differential housing had all three broken loose. That's a Bad Thing(tm), and usually indicates that the axle tube has flexed pretty severely. This is a common problem with the D35 axle. When the tubes flex, the axle shafts are no longer parallel, which causes all sorts of problems inside the pumpkin.

    When I got around to opening up the diff, my fears were confirmed. First, the gear that ran out when I cracked the cover was silver, not brown. It appears that when the tubes flexed, it distorted the LSD carrier and snapped two teeth off the spider gears. I didn't notice the problem at slow trail speeds, and since I flat-towed the YJ back home behind my '77 Wagoneer, I couldn't hear any noises that may have been emanating from the YJ's rear axle. The teeth apparently got thrown around pretty violently inside the diff, because I was also missing the corner of one of the pinion gear teeth, the Trac-Lok carrier had some large (but cosmetic) divots taken out of it, and the inside of the diff cover was scraped and chunked up pretty badly. When I tried to remove the axle shafts to inspect them, I found that the threaded pin that holds the spider gear cross shaft had broken, no doubt due to the shock stress on the spider gears. That's a fair amount of damage even if the axle shafts are good, so I decided to write off the entire axle assembly and replace it with a new, stronger one.


  4. #4
    Some more info for ya, everything you wanted to know about putting an 8.8 in a ZJ:

  5. #5

    Technical info about 8.8 conversions Page-4

    Since I was short on time and didn't really feel like swapping gears in a pair of Dana 44's and upgrading both axles at the same time, I opted to take the quick and easy (as axle upgrades go) route and install a Ford 8.8" rear axle from a 1995-2001 Ford Explorer. This axle has many good points:

    * It's at least as strong as a Dana 44, and is generally plenty strong for anything less than a built V8 engine. Ford has used this axle to replace the venerable 9" in Mustangs and F-150's.
    * It's got 1.31", 31-spline axle shafts, compared to the D35's 1.16", 27-spline shafts. Like the D35, it does use C-clips to retain the shafts, but you'd have to break one of these beefy shafts before that becomes an issue.
    * It has an 8.8" ring gear (go figure), compared to the D35's 7.5" gear.
    * The tubes are 3.25" in diameter, compared with the 2.5" D35 tubes. The 8.8 tubes do neck down to 2.75" just before they enter the brake housings.
    * It comes with 3.55, 3.73, or 4.10 gears from the factory -- all three of which are common ratios for stock, late-model Jeeps. If you're still running stock gears (like I was), it's quite likely that you can upgrade to this axle without having to do a gear swap.
    * It was available from the factory with a Trac-Lok limited slip differential. Many junk yards call this a locker, so don't be confused.
    * It's 59.5" wide (between wheel mounting surfaces), compared to 60.75" for a YJ D35 (the XJ/MJ/TJ are nearly identical). This will move your rear tires inward 5/8" per side, which isn't really an issue unless you're still running the stock wheels with their whopping 5.25" of backspacing.
    * It has a 5x4.5" wheel bolt pattern, which is the same as
    * The gear oil fill plug is on the front of the housing instead of in the diff cover. If your pinion is pointed skyward for a CV driveshaft, you can now full fill your pumpkin without parking on a hill.
    * The above all apply to all 1991-2001 Explorer axles, but beginning in 1995, they also had disc brakes. A rear disc brake swap on most drum-equipped axles costs at least $450-600 by itself.

    The Ford 8.8" does have some drawbacks:

    * The axle shafts are held in by C-clips, just like the Dana 35. This requires opening and partially dismantling the differential in order to remove the shafts, and if you brake a shaft (which is more unlikely given their beef), there's nothing to hold your wheel onto the axle housing.
    * Rather than welding the tubes into the diff housing, the tubes are just held in with pressed-in plugs. These plugs tend to stop doing their job under severe stress, so you really should weld the tubes to the housing with low-hydrogen rod while you've go the welding gear out. Check out this article at JeepWire.Com for more details.
    * The selection of gear ratios and lockers for the 8.8 isn't as large as for the Dana 44. In a perfect world, I'd install 5.13 gears someday, but 4.88 is as low as I can go with a D30/8.8 combo.
    * The factory diff cover is made of tin foil. After market covers are available.
    * The pinion is offset a whopping 2-3/16" to the right of center, compared with 3/4" for the Dana 35. This additional 1-7/16" of offset on a 17" driveshaft makes a horizontal angle of 4.8 degrees at the pinion U-joint. This isn't a big deal with a stock, single-cardan driveshaft, but with a CV driveshaft, that kind of angle can potentially eat U-joints and cause driveline vibrations. M.O.R.E. claims this hasn't been a problem in their experience. We'll see.

    Another thing that makes this swap easy is the fact that M.O.R.E. offers several kits to install this axle in a Jeep YJ/XJ/TJ. The one includes all the mounting hardware and spring plates, and another includes new e-brake cables that will hook up properly at both ends. I emailed M.O.R.E. several times when planning this swap, and they were always quick to reply with detailed answers to my questions. Great folks.

    One thing to note is that the 8.8 uses a pinion flange instead of a pinion yoke like most Dana axles. Spicer makes adapters (called "flange yokes") that connect this flange to larger 1330-style U-joints (1994-95 YJ's) or smaller 1310-style U-joints (most other XJ/YJ/TJ's). The 1310 yoke is Spicer part number 2-2-1379. The 1330 yoke is P/N 2-2-1369. I'm told that the stock Explorer driveshaft uses a 1330 joint, so you can grab the adapter from your axle donor if that's the size you need. These adapters bolt to the pinion flange with 12mm x 1.75 thread bolts. The 12-point factory bolts are Ford P/N N800594-S100. I picked up four 25mm-long, grade-5 bolts & lock washers from the corner hardware store.

    Normally, disc brake calipers require more fluid to activate them than do drum brakes. That's why the two containers in a stock YJ master cylinder are different sizes. Although it would seem that you would want to change at least the proportioning valve and possibly the master cylinder when adding rear disc brakes, it is reported that the stock YJ setup works well with the Exploder disc brakes. I heard it suggested that perhaps the proportioning valve from a ZJ/WJ (which came from the factory with rear discs) might work even better, but I don't know anybody who has confirmed this.

    Since the 8.8's tube diameter is 3/4" larger than the D35, your rear end will probably either gain (SOA) or lose (SUA) 3/8" of lift height after the axle swap. In my case, my old D35 spring perches sat about 3/8" taller than the stock Exploder spring perches that I used on the 8.8, so it all evened out. YMMV.

    How I Did It

    (New Axle) I called around some nearby salvage yards, and the best price I could find also came from the only place that had one with 4.10 gears and an LSD. I paid $400+tax to Hansen's Truck Salvage in Omaha, NE (about an hour's drive from my house) for an 8.8 from a 1996 Explorer (VIN 1FMDU34X9TZA31483 -- perhaps 1FMDU84X9TZA31483?). They claimed it had a locker, but it's really just the factory limited slip. A non-LSD axle would have cost just $300. Incidentally, you can search the inventory of many salvage yards (including Hansen's) online at

    They told me over the phone that the brakes were in fine shape. However, when I got there, I found that the rotors were quite rusty, both soft brake lines to the calipers had been cut, and the hard line that ran along the axle tube was missing. When I turned the axle shaft by hand via the wheel lugs, it made some scraping noises, but that went away after I removed the calipers and rotors.


  6. #6

    Technical info about 8.8 conversions Page-5

    The next day, I took a bunch of measurements (for comparison purposes), inspected the pumpkin innards, and removed the original spring and sway bar mounts from the axle.

    (Gears/Carrier) The inside of the differential looked fine, aside from containing rather dirty gear oil. It had already been mostly drained by the salvage yard. It does have 4.10 gears. It does indeed have a clutch-type limited slip differential, although I couldn't find any identifying marks on it. The top of the housing has an electrical connector on it that's used by the Exploder antilock brake system. This sits right above the back side of the ring gear, where the ABS tone ring is mounted.

    Removing the original spring and sway bar mounts from the axle tubes was straightforward. I don't own a cutting torch, so I instead used a 4.5" angle grinder and two cutting disks, as well as the obligatory BFH. I used the grinder to cut through the weld beads and about half way through the thickness of the mount, then I beat on each end of the mounts with a BFH to finish breaking the weld beads and knock the mounts away from the axle tubes.

    (Spring Perch) (Grooves) (Clean Tube) (Both Axles)

    Although the mounts were removed in pretty good shape (I was able to reuse the spring mounts), the cutting wheel dug a little deeper into the axle housing than I would have liked (the worst was still less than 1/8" deep). Ideally, all the material removal would have been from the mounts themselves so as not to compromise the strength of the tubes. I filled in the cuts in the tubes with my welder just in case.

    Once the mounts were removed, the remaining metal was smoothed out with a grinder. I used a wire wheel on a drill to remove rust, crud and loose paint from the rest of the axle, then an electric sander with 60-grit paper to clean the last of the old paint from the tubes. This made both welding and painting much easier.

    As mentioned earlier, the brake rotors were extremely rusty. Not just any shop can turn rotors that have an integral drum-style e-brake, so I had to take them to Lincoln Clutch & Brake. It turned that that there was a 0.1" difference in the thickness of the two rotors. Minimum spec on these rotors is .409". One of my rotors was .460", so they turned the rotor part for $8 (they would have turned the drum for another $5, but they said that's usually not necessary for just an e-brake). The other rotor, however, was only .360" thick, so I had to replace it with a new one.

    I ended up not buying M.O.R.E.'s kit with all the brackets stuff. I found that it was cheaper and faster to just find the stuff locally. I reused the stock spring perches from the 8.8. I'll be installing a ladder bar, so their anti-wrap perches aren't a necesity for me now. I obtained a pair of stock Exploder spring plates from junk yard for $20 and cut off the factory shock mounts. I got new U-bolts custom made for $27. I bought new lower shock mounting tabs from Speedway Motors (they're local for me) for $9. $56 vs $122+shipping isn't a bad tradeoff. I realized after the whole swap was done that I probably could have just reused the factory Exploder shock mounts that I cut off the spring plates. It would have been free, and would have saved me having to weld the center brace onto the Speedway mounting tabs. Live and learn.

    (Upper Shock Extension) (Lower Shock Mount) I did order a new set of upper shock mount extensions from M.O.R.E., however. My old shocks were sized perfectly for the stock mounts, the lower of which hang about 3" below the bottom of the axle. To improve clearance, I welded the new mounts up so the bottom is flush with the bottom of the axle tube. The M.O.R.E. upper mount extensions add 2.5" of length to the shock, which allowed me to keep my current shocks while moving the mounts up out of harm's way. Installing these shock mounts kind of took on a life of its own, so I've written up a separate page detailing the ordeal. The net result was that my shocks are now 3/4" shorter at rest, but that should be OK, because they now sit at a lower angle and therefore don't need to compress as far when the axle rises. The additional clearance under the axle should come in handy.

    Removing the old Dana 35 from the Jeep was pretty straightforward once I figured out how to disconnect the e-brake lines from inside the drum brakes. You know the axle's wimpy when I can dead lift it across the driveway. I bolted the Ford 8.8" in place, then centered the axle, reinstalled the wheels, and lowered the Jeep's weight onto the rear wheels. I put a bit of weight in the rear end to simulate a normal load and then jumped up & down on my rear bumper to get the Jeep's suspension back down to its normal ride height. Then I set the pinion to the proper angle for my CV driveshaft (2 degrees shallower than the driveshaft) and positioned the lower shock mounts where I wanted them. I then tack welded all the mounts in place and finally removed the axle again so I could finish welding the mounts in the wide open. Tack welding the perches while lying on my back under the running Jeep was made much easier by my new auto-darkening welding helmet ($60 on eBay). Having to flip a standard helmet up & down while lying under there would be quite a pain.

    The brake line configuration had to be completely redone. The factory Exploder setup has the soft lines (to the calipers) bolted to threaded holes in the end of the spring perches. The Exploder frame-to-axle hose is an integral part of the left side soft line to the caliper. On an SUA Jeep, you could keep this same setup and use aftermarket extended brake lines for an Exploder. On an SOA Jeep linke mine, this won't work. What I did was use two right-side soft brake lines. I secured these lines to the axle tube by welding a 1/4"-thick tab to the axle tube right behind each spring perch. These tabs have one 3/8" hole for the brake line's locating tab and a threaded hole for an 8mm-1.25 bolt that's used to attach the brake line fitting. After painting the axle, I routed the hard brake lines along the top of the axle tube & pumpkin and joined them with my older, braided SS AN4 soft line to the frame using a 3-way junction block near the vent tube's threaded hole.

    Because I didn't want to do all this work and then have a rusty old axle hanging under my Jeep, I wiped everything down with brake cleaner, coated everything with Krylon "Rust Tough" galvanizing primer (designed for marine and other corrosive environments), then painted it all with Rustoleum semi-gloss black enamel. The pinion flange and spring plates got the same treatment. Just to add a little accent, the calipers were painted with metalic silver instead of semi-gloss black. The whole assembly required two full 12oz cans each of primer and black enamel. Since I was doing this in an enclosed garage (too cold & windy outside), a gas mask was invaluable. BTW, even with no breeze, rattle-can enamel will coat everything in the room with a light film. It happened when I painted my engine, and it happend again with this axle.


  7. #7
    Wally's Avatar
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    Jan 2003
    Snowmass Village / Grand Junction, CO
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    Good stuff, i might add that it's been tested multiple times and the stock 8.8 31 spline shafts are over 33% stronger than the stock 30 spline dana 44 shafts

  8. #8

    Technical info about 8.8 conversions Page-6

    POR-15 is reputed to provide a rock-hard surface that's impervious to future rust. I've used it before with good results, but I've also found that while it sticks like glue to rusty surfaces (and bare skin), it doesn't adhere very well to well-painted surfaces or to shiny, bare metal. Whenever I've tried to apply it to shiny metal, it's flaked off in large sheets. Since almost all of my new axle was either painted or shiny, I opted for conventional paint this time. Time will tell how well it holds up. I'm hoping the galvanizing primer does its job (at $6 per 12oz can, it had better).

    Once the paint was dry, it was time to assemble the brakes. The brake shoes on the e-brakes were shot, so I had to replace those. Man, what a pain. I hate working on drum brakes. At least the e-brake-only drums are considerably less complicated than the hydraulic drums on most rear axles. I had to bend a new hard line, since the original one was missing and probably wouldn't have been ideal anyway. A 48" length of 3/16" tube left about 6" to spare. I secured the hard line to the axle using the factory method -- one metal strap welded to each tube and then bent over the hard line, plus a third strap bolted to a threaded hole in the top of the pumpkin with a 5/16"-18, 1/2" long bolt. I cut and double flared the hard line near the vent hole, since that was a convenient location for the junction block on my existing braided SS line up to the frame. O'Reilly Auto (Midwest chain) loans out double flare tools for free with a $43 deposit.

    With everything assembled, bolting the axle in place was straightforward. When bleeding the brakes, it was obvious that the rear brakes aren't getting nearly as much fluid pushed to them as the front brakes are. The 8.8's calipers are noticeably smaller than the D30 calipers up front, but I still wonder if maybe an adjustable proportioning valve would help out a bit. I'm told that the stock YJ valve generally does a sufficient job already. On the test drive, the brakes stopped noticeably faster than before, so I guess the current setup is good enough for now. My suspension is soft enough that the Jeep nosedives badly long before my tires lock up, so I can't easily empirically test stopping distance.

    (Ford 8.8 Install) (Ford 8.8 Install) (Ford 8.8 Install) (Ford 8.8 Install) (Ford 8.8 Installed) (Driveshaft Offset)

    Merry Christmas to me! For the first time in over a month, I got to drive my YJ on Christmas Eve. Still didn't have e-brakes yet and the air tank for my compressor was still disconnected, but at least it moved under its own power. It's got some bad vibes when accelerating from a dead stop, which I imagine is due to the pinion being offset 1.5" farther to the right than the t-case output. That offset with a 17" driveshaft creates an angle of about 4 degrees, which is quite a bit higher than I would have wanted with a CV driveshaft. This wouldn't be an issue with a standard, single-cardan driveshaft. I don't get vibes when cruising, so the 4-degree angle isn't bad by itself, but when the pinion climbs under torque, the combined angle is too large. That's my theory, anyway. We'll see if it goes away when I install my ladder bar.

    The last thing to hook up was the emergency brake cables. The rear ends of the stock YJ cables aren't designed to mate up to the e-brake levers on the 8.8". M.O.R.E. makes conversion cables that have the proper connections at each end, and are a few inches longer to help with lifted Jeeps. The D35 e-brake connection is at the bottom of the drum, while the 8.8" e-brake lever is at the top of the brake, so I don't think the extra length is really necessary.

    I opted not to spend $120 on the M.O.R.E. cables. Instead, I modified the stock YJ cables to work. I basically put a 1/8" cable thimble around the 8.8" e-brake lever, cut about half the spring off the YJ cable, then looped the bare cable around the thimble and fastened it back to itself using a cable lock. The ball at the end of the YJ cable prevents it from pulling through the cable lock. I had to use 3/16" cable locks instead of 1/8" locks because the 1/8" U-bolts weren't long enough to get the nuts threaded on. The most time consuming part was removing 2/3 of the return spring from the cable. You want it to just touch the end of the cable lock when it's not compressed, so that it will help push the brake lever to the "free" position when you release the e-brake pedal. I unwound one of the springs with pliers, but I cut the other one off by running a dremmel tool the length of the spring on both sides. Cutting it off was faster, but not by much. I had to unscrew the e-brake adjusting nut where the cables meet at the frame rail about 1" farther than before in order to free up enough cable at each wheel to wrap it around the thimble. I also had to cut about 3/16" off each of the lock tabs where the cables attach to the axle end, since the bracket on the 8.8" is much thicker than the one on the D35. Viola! Stock YJ e-brake cables connected to a Ford 8.8" for less than $3 in hardware.

    (E-Brake Cable) (E-Brake Cable) (E-Brake Cable) (E-Brake Cable) (E-Brake Cable)

    Now that it's all done, what would I have done differently? Most of this was learned the hard way during the swap.

    * When drilling the holes for the new upper shock mount extensions, I should have skipped the cutting oil and enlarged the drill bit size in very small increments.
    * I should have used the shock mounts that I cut off the spring plates rather than buying/making a new pair.
    * When cutting the old perches off the axle tubes, I should have been more careful to not cut into the axle tubes with the grinding wheel.
    * I should have used high-nickel welding rod from the get-go when welding the tubes to the pumpkin. Yeah, it's pricy ($2/rod). Live with it.
    * When welding the tubes, I should have tack welded several spots around the tube circumference and then filled in the gaps evenly rather than working my way around the tube in a continuous line. The former method is less likely to warp the tube.
    * I should have masked off the wheel studs prior to painting the axle. Installing the lug nuts to the proper torque was a pain.

    Hopefully this has helped you with your 8.8 Questions/Install - BikeGuy


  9. #9
    Mark's Avatar
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    Fort Collins
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    Quote Originally Posted by Wally View Post
    Good stuff, i might add that it's been tested multiple times and the stock 8.8 31 spline shafts are over 33% stronger than the stock 30 spline dana 44 shafts
    Not that I'm arguing this, but do you have a link to test results?

  10. #10
    Mark's Avatar
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    Fort Collins
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  11. #11
    Quote Originally Posted by OlBlueCJ7 View Post
    Not that I'm arguing this, but do you have a link to test results?
    The axle shaft strength (tested by Warn Ind.) is as follows:

    F8.8= 6,500 (lb. ft.)

    D44= 4,600-5,000 (lb. ft.)

    D35C= 4,000-4,300 (lb. ft.)

    Sorry, I do not have D60 or F9" shaft strength.


    Axle shaft Strength and output torque rating by 4 Wheeler
    (Numbers from January edition of Fourwheeler, page 60.)
    Dana 35 rear axle COT: 870 MOT: 3480
    Dana 44 rear axle COT: 1100 MOT: 4460
    Ford 8.8 28spline COT: 1250 MOT: 4600
    Ford 8.8 31spline COT: 1360 MOT: 5100
    Dana60 semifloat COT: 1500 MOT: 5500]

    This was all listed on this Tech Thread.


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