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  1. #1
    DaneH's Avatar
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    What motor and transmission would you go with?

    I have a 2003 TJ Rubicon - at least it used to be. I have a set of built one ton axles that will be going under it soon (Snowfighter in the front, Spidertrax 9 in the rear). I have an Atlas 2 t-case already. Due to some financial change in plans, I should now be able to swing a nasty engine to pair with it. I don't have a set budget at this point, but I don't have to go cheap, and I would like to put some nasty power under is (6-700hp). Do I NEED that, nope, but that's what I'd like to do for a variety of reasons. I'll be keeping the rig street legal for the occasional time it needs to be on the road, but it's not a daily driver. The question here is what motor and tranny would you put in there?

    I'm leaning towards a built LS motor and a 4L80, but I fully confess that the ins and outs of motors and transmissions are not my specialty. There are a million flavors of LS motors out there, and I'm pretty green there, so I'm looking here for wisdom and guidance in this area. I know there will be a lot of computer and gauge issues to tackle. I'll also have emissions hurdles to deal with. I'd like to get this all mapped out so I don't paint myself into a corner due to lack of research.

    The rig is already half-backed with a fuel cell where the rear seats once were. During this next phase we'll be cutting the frame off from the cab forward to tube it out - therefore engine fitment shouldn't be a big deal.

  2. #2
    newracer's Avatar
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    Have you ever seen a man eat so much fish?

  3. #3
    I’m thinking hard about an an Ls with a 6L80 behind it. For some reason I’m very intrigued by 6 gears. 6-700HP should be doable with some massaging and it sounds like the rest of your drivetrain is up to it.

  4. #4
    The Original Opie-Gone-Bad!!! Aaron's Avatar
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    You can not go wrong with a turn key engine from Texas Speed

    https://www.texas-speed.com/c-3188-a...d-engines.aspx

  5. #5
    DaneH's Avatar
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    Quote Originally Posted by YJLopes View Post
    I’m thinking hard about an an Ls with a 6L80 behind it. For some reason I’m very intrigued by 6 gears. 6-700HP should be doable with some massaging and it sounds like the rest of your drivetrain is up to it.
    I'm actually now thinking about the 6L80 instead. Thinking that's my direction, so interesting that you mentioned it.

  6. #6
    DaneH's Avatar
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    Quote Originally Posted by Aaron View Post
    You can not go wrong with a turn key engine from Texas Speed

    https://www.texas-speed.com/c-3188-a...d-engines.aspx
    This is interesting. Having some fun on this site. May have to give these guys a call.

  7. #7
    That is a bunch of power that you will rarely use and pay dearly to obtain.

    Reliability is important in what we do. LS motors are tight and run well at extreme angles. Think 6.2L with the 6L80E paired to it. All stock with a reverse shift pattern and electric fan. Hydro steering with large hydraulic capacity and coolong. If you want more power put a 4 speed atlas and utilize the 2:1 for sand and snow and the 5.44:1 for crawling. 2.72:1 is kind of useful but really just gives an extra option and gets you to the 5.44:1.

    Yes the power and roar will make you smile when you light it up, but think of everything and i mean EVERYTHING that will need to be beefed up with 6-700hp.

    Tried and true, have fun and make it home or back to the truck at the end of the day.
    Last edited by Impaired; August 4th, 2021 at 06:33 PM.

  8. #8
    DaneH's Avatar
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    Quote Originally Posted by Impaired View Post
    That is a bunch of power that you will rarely use and pay dearly to obtain.

    Reliability is important in what we do. LS motors are tight and run well at extreme angles. Think 6.2L with the 6L80E paired to it. All stock with a reverse shift pattern and electric fan. Hydro steering with large hydraulic capacity and coolong. If you want more power put a 4 speed atlas and utilize the 2:1 for sand and snow and the 5.44:1 for crawling. 2.72:1 is kind of useful but really just gives an extra option and gets you to the 5.44:1.

    Yes the power and roar will make you smile when you light it up, but think of everything and i mean EVERYTHING that will need to be beefed up with 6-700hp.

    Tried and true, have fun and make it home or back to the truck at the end of the day.
    I hear you, and I've thought about it. I'm running an Atlas 2 with a 4.3 ratio which should be able to handle this. I opted out of the 4 speed since it's actually weaker. Front end is a beefed up Snowfighter Dana 60 with 40 spline RCVs and a bunch of other goodies. Rear is a brand new Spidertrax with a Gearworks 10" third member including competition 40 spline ARB. Driveshafts are already beefed up for this, but will receive a bit more tweaking and should be good. I already have hydro assist and hydro boost in boxes in the garage waiting to go in, but since it will be driven on the street here and there I'll be sticking with hydro assist.

    I realize it's overkill, but that's what I'm after. I plan on keeping this Jeep forever. 6.2L and 6L80 is exactly what I'm looking at, though likely a built 6.2. Agreed on the electric fan. The Jeep is currently a manual (as all of my wheeling rigs have been), so other than my truck that only sees pretty easy offroad stuff this will be my first time wheeling hard stuff with an automatic. What's the reason for the reverse shift pattern?

    Also, cooling is going to be a main focus of mine through the build.
    Last edited by DaneH; August 5th, 2021 at 09:58 AM.

  9. #9
    The reverse pattern puts 1st gear and reverse close together on the shift pattern for quick transitions in sketchy situations. I didn't have it on all my set ups, and would end up cutting gates out of the Art Carr shifter to be able to "slap" the shifter into reverse.

    Reverse Pattern
    https://www.polyperformance.com/pub/...432_edit_6.jpg

    vs.

    Standard Shift Pattern
    https://www.polyperformance.com/pub/.../image-2_1.jpg


    I have broke the 4-speed Atlas, but I think it was an initial assembly failure more than anything as I was harder and harder on it as I got more comfortable with it. The tail shaft yoke was next after internals failed and both of those were my fault being silly. Warrantied the internal damage though without question or issue.
    Last edited by Impaired; August 9th, 2021 at 05:32 PM.

  10. #10
    DaneH's Avatar
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    Quote Originally Posted by Impaired View Post
    The reverse pattern puts 1st gear and reverse close together on the shift pattern for quick transitions in sketchy situations. I didn't have it on all my set ups, and would end up cutting gates out of the Art Carr shifter to be able to "slap" the shifter into reverse.

    Reverse Pattern
    https://www.polyperformance.com/pub/...432_edit_6.jpg

    vs.

    Standard Shift Pattern
    https://www.polyperformance.com/pub/.../image-2_1.jpg


    I have broke the 4-speed Atlas, but I think it was an initial assembly failure more than anything as I was harder and harder on it as I got more comfortable with it. The tail shaft yoke was next after internals failed and both of those were my fault being silly. Warrantied the internal damage though without question or issue.
    Gotcha. Builder guy I've been working with had suggested that, just hadn't called it that. Reverse shift pattern is the plan.

  11. #11
    DaneH's Avatar
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    Continuing my research a bit here - can anyone recommend a local Denver area (south Denver would be great, but not required) engine builder I could talk to? I'd like to explore the build versus buy option just so I feel like I have covered my bases. I also have some emissions concerns with a few create type motor places I have been talking to.

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