It is Time to Swap -
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post #1 of 3 Old 12-30-2007, 05:12 PM Thread Starter
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Recoil's Avatar
1988 MJ Comanche 
Join Date: Oct 2007
Location: Indiana
Posts: 1,863
It is Time to Swap

So I finally have a six to put in place of my current 4 banger. Other than an AX15 what else to I need and is there a current "thorough" write up of this being done on a TJ? Is there going to be an issue that the 6 is out of an '05 and my Jeep is a '98

Current set up:

1998 Wranger SE
All stock suspension
2.5l 4 cyliner
AX5 trans
NP231 Transfer case
Dana 30/35 stock set up
4:10 gearing
No A/C

what else could be an issue that I might run my lack of A/C going to be an issue with the PCM?

Last question: does anyone know if 2005 Rubicons (the donor vehicle) came with the security feature on the PCM?

Here we go Ill start my build thread soon. Have done quite a bit to the peej so far but nothing to really scream about either way youll see

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post #2 of 3 Old 12-30-2007, 06:39 PM
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1996 XJ Cherokee 
Join Date: Mar 2007
Location: Noblesville
Posts: 5,487
Dude I still can't believe you scored that for free! Lucky f*cker! I'll have to do some research for valve sizes and such, I may just swap you for your stock head and pay for the bigger valves, valve springs, rockers, ect. to rebuild mine(no that doesn't include roller rockers!), and you put the good stuff on yours, since your stroking it, can always build my engine at a later date.

My guess is XJ springs in the front and LJ springs in the rear wouldn't hurt, don't know if the SE springs are different than X/Sport/Sahara/Rubicon springs but I'd guess for a heavier engine, they'd have heavier rated springs plus get a cheep lift at the same time.

96 XJ:
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89 MJ: Project: Ground up - Sold
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***** inches...
Good god man. Indyorv :rofl: d**k and fart jokes. :rofl:
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post #3 of 3 Old 12-30-2007, 07:12 PM
KTM Mike
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1997 TJ Wrangler 
Join Date: Oct 2004
Posts: 25
98 - I am in the middle of the same swap (well, not middle...uh, first 1/4?) has a lot of good info. This forum has a few as well. I found few detailed write ups specifically on TJ 2.5 to 4.0 swaps - most were YJs. Here are a few tidbits I did learn

- Your T-case is 21 spline - you need to convert it to 23 spline, or buy a different T-case
- I think there were some electrical changes in 01 or so on the TJs - I suspect you can make your ECM work, but might have more trouble than if using something pre 01. Some sort of changes with how the ECM communicated with the guages or something?
- According to the Novak site - no changes in springs really needed - I would think there would be a need though. Time will tell. I have a Rancho lift and their springs were a bit stiffer than stock, so I might be Ok.
- I think (hope) you will be Ok with no AC - I dont have it either, yet my 4.0 ecm does - i believe you simply dont wire in anything on that circuit - no issue?
- You will need to relocate the weld on part of the motor mounts, using 4.0 mounts. Seems best bet is order them new.
- Your gearing with 4.10s will be great for some taller tires , with stock size tires, you will be spinning the 4.0 up a bit higher RPM. I think stock 4.0s have 3.57 or in some cases depending on tranny, even 3.07 gearing.
- I would bet that the 05 Rubi ECM has the SMART Key/SKIM stuff enabled. from what I understand, that crap started in 98 on some models but not all. Higher end models more than likely have it, and the newer it is, the more likely to have it. You have both...newer and higher end trim level. That alone might be a big road block. I got lucky - I am using a ECM from a 98 Grand Cherokee which did not have the SMART KEY stuff! Find out what the ignition key from the donor looked like. Grey end - SMART Key, Black end...not! Hope for black!
-Drive shaft length might be different. AX5 is shorter than a AX15. In my case I am using an AW4 - so definetly will deal with drive shaft issues.
- DO LOTS of google searches! Do LOTS of searches on any Jeep/Offroad forums you can find! Here is a link to some pics of an install in a TJ - I cant find the link to this guys post on Pirate4x4 - but he did a brief write up in a thread there. Good pics of the motor mounts location (though from what I read, best bet is to hang engine in place, pin down location that way - not trying to use measurement.
- Here is a link to a thread I started on the Michigan Wheelers forum - I will be updating it from time to time.

Best of luck! I look forward to reading some new threads on this!

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