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Auto Transmission Swap Compatibility

QuillsXJ

NAXJA Forum User
Location
California
Question on swapping a new (used) auto trans into a 98 Cherokee: are all year Cherokee auto trannys a direct swap considering the ECU, driveline, etc.? What is the best auto trans out of all the years?

Thanks guys!
 
If I remember right and no guarantee there... The 97+ AW4s are different. I think it is due to the late models having an input and output shaft speed sensors whereas the early only had an input shaft sensor. Could be wrong. Check the AW4 thread out. Has most everything there is to know that is worth knowing. Different TCMs as well...
 
For straight bolt-in I would say 97+ aw4 91-96 would work but would need to make sure you have correct sensors and stuff.
 
90 and earlier won't work without a significant rebuild and parts swapping.
91-97 won't work without a fairly significant rebuild and parts swapping, less than 90- but not easy.
98-01 are bolt in.

More detailed info: http://www.naxja.org/forum/showthread.php?t=1053970

Make sure you get one that's the proper 2wd vs 4wd version. Converting back and forth from 2wd to 4wd is as difficult as converting from a 90 and earlier to fit a 98 and later, not for newbies, unless you really want to do a rebuild that is more complex than simply rebuilding your existing transmission.

You can make a 91-97 trans (slight wiring differences across those years, but nothing complex) work with a 98 and later if you pull a 97 (only 97, make sure the part number is 5602 7951) TCU and install it and do some wire splicing.
 
90 and earlier won't work without a significant rebuild and parts swapping.
91-97 won't work without a fairly significant rebuild and parts swapping, less than 90- but not easy.
98-01 are bolt in.

More detailed info: http://www.naxja.org/forum/showthread.php?t=1053970

Make sure you get one that's the proper 2wd vs 4wd version. Converting back and forth from 2wd to 4wd is as difficult as converting from a 90 and earlier to fit a 98 and later, not for newbies, unless you really want to do a rebuild that is more complex than simply rebuilding your existing transmission.

You can make a 91-97 trans (slight wiring differences across those years, but nothing complex) work with a 98 and later if you pull a 97 (only 97, make sure the part number is 5602 7951) TCU and install it and do some wire splicing.

This makes me wonder how the mechanically uninclined previous owner of my 97 country swapped in the aw4/242 from an 88 and it works (somewhat). I'm still on the look for a 97+ aw4/231 to get and put back in so it's the correct setup.
 
Okay, yeah this would be a 2wd transmission swap. So the whole story is there is a 98 Cherokee on Craigslist a guy is willing to sell me for $1k but he is claiming that one day he was driving it and the transmission just quit and he had it hauled to a trans shop and they told him he needed a trans replacement. There is no CEL code being thrown. Personally I am willing to get into this and do a rebuild because the Jeep is in almost perfect condition otherwise and has 148k miles. I find it hard to believe that the trans currently on the Jeep is beyond repair. The engine starts and runs fine. What would you suspect failed on the trans given these conditions?

Thank you!
 
I was told I needed a new tranny on my 90 XJ by a local tranny shop. Turned out the fluid was low because of a tranny hose leak. That was 130K miles ago. Still running.

I'd get a second opinion, from someone you trust and knows something about Jeeps/trucks. Check the fluid level. Check the color, should be red. A non-running XJ might be worth $1000.
 
Aw4 will take anything thrown at it. Id agree get a second opinion. If the jeep is clean ot could very well be worth over 1k parted out
 
This makes me wonder how the mechanically uninclined previous owner of my 97 country swapped in the aw4/242 from an 88 and it works (somewhat). I'm still on the look for a 97+ aw4/231 to get and put back in so it's the correct setup.
That swap is 100% possible, I think I remember your thread asking about what tcase spline count you had and stuff. A 97 has the same sensor electronics and stuff (aside from the NSS, which bolts onto the outside) as an 88 electronically so just a few simple splices and it plugs into the harness. If it only works somewhat, they had no idea what they were doing. Worst case, you'd have to swap the throttle valve cable, I am not sure if the RENIX era one used a goofy bellcrank or went straight to the throttle arm.

It's a dumb swap because you end up with a 21 spline setup when you could get a 23 spline one easier, but it works. It is the 98 and later jeep with 97 and earlier tranny (hardest, unless you swap TCU) or 97 and earlier jeep with 98 and later tranny (not hard if you don't mind screwing around with some stuff or soldering some things) swap that is difficult.

Okay, yeah this would be a 2wd transmission swap. So the whole story is there is a 98 Cherokee on Craigslist a guy is willing to sell me for $1k but he is claiming that one day he was driving it and the transmission just quit and he had it hauled to a trans shop and they told him he needed a trans replacement. There is no CEL code being thrown. Personally I am willing to get into this and do a rebuild because the Jeep is in almost perfect condition otherwise and has 148k miles. I find it hard to believe that the trans currently on the Jeep is beyond repair. The engine starts and runs fine. What would you suspect failed on the trans given these conditions?

Thank you!
Oh, cool. Buy a 4x4 one from a 98-01, an NP231 from a 96-01, and a rear driveshaft from a 96-01 with the same rearend, bolt it all in, and you are now that much closer to a 4x4 swap whenever you feel like it!

That is, if the tranny is even bad. I would be somewhat surprised if it is - wish I was closer, I'd be in for a test drive/debug session before purchase.
 
Thank you for your help you guys! Kastein, what are the typical fail points on this type of transmission? Like what would fail and not throw a code? A short list of suspected fail points would be extremely helpful to me.

Things I will do so far based on my experience:

-check to make sure CEL light is operational, first and foremost
-cycle through gears on shifter to check for shifting
-check all trans relays and fuses
-check adjustment & integrity of trans kickdown cable
-check TPS on throttle body
-check to make sure torque converter is bolted (bolts aren't broken) to flywheel through bell house viewing cover
-check trans fluid level & quality, check for leaks around pan, drain fluid and check for debris
-check trans cooling lines are intact without leaks
 
Your list sounds good as a starting point.

Next thing you can do is try unplugging the harness connector for the TCU - it's on the driver side of the trans tunnel up under the dash. Little square metal box. If it runs and drives but shifts manually only, and only has 1st, 3rd, OD, park/neutral, and reverse, with no tq lockup, the issue is electronic in nature. If it drives but very sluggishly in D, try putting it in 1-2, it should be better.
 
I ended up purchasing the Jeep this weekend. The Jeep had been sitting for about 5 years. The seller “conveniently” didn’t have a battery in the Jeep or around that I could use to start it to hear the engine run and then to test how the transmission, so he claimed, failed. So being overly confident and taking some chance I trailered it home and got a new Costco battery and installed it. The starter and engine crank, but I am not getting any ignition. Less than a day of diagnosis and testing my no start my results are:

-All gauges and accessories appear to be working when key is turned
-No check engine light; pulled off dash and checked bulb it was fine but swapped bulb with working check gauges bulb to be 100% certain
-Replaced CPS for 100% certainty, old CPS seemed like it had been replaced not too long ago (weird).
-For maintenance and process elimination purposes, I replaced the distributor cap, rotor, plugs, and wires with new.
-Pulled a plug and grounded to Jeep frame and checked for spark, there is spark.
-Checked every fuse in engine fuse box, swapped relays for the ASD and Fuel Pump.
-Checked and wire brush cleaned every ground wire and bolt: engine fuse box, firewall, engine block, and the grounds behind the alternator.
-Checked fuel pressure manually at fuel rail and there is no pressure and can’t hear the pump prime in the fuel tank.

I am open to any ideas that I should try to get the engine running. If someone could rule out or add to my list of things I am about to try next it would be appreciated.

-Identify a safe way to test that I am getting fuel to the fuel rail and that my pump works. Is there a safe way to jumper the fuel pump?
-How would I test the ASD circuit? If this failed would this cause no start or would it cause start and stall?
-Install new battery +/- cables? My connections at the terminals feel a little loose.
-Could the crankshaft position sensor have failed?
-Why when I disconnect the TPS or another sensor and try to start does the CEL not come on?

What was interesting was before I replaced the CPS I had no working fuel gauge indicator and after my fuel gauge now works and shows a half of a tank of gas. Maybe this was because the ECU reset?

I feel like the problem with the Jeep may not even be the transmission at all based on what the guy described to me. He described a power cut while he was going 80+ down the freeway once. He also described other instances of loss of power while driving and then it finally had nothing and he had to tow it to a shop.
Anything would help or other suggestions.
 
diagnose no fuel

either the pump runs or not..
if not why not? is it getting 12v during crank? is the ground good? damage from water in the tank?

if it runs; but no fuel pressure why not?.. internal fuel leak? pump damaged from sitting in water/bad 5 year old fuel?
 
How and where do you safely diagnose the 12v on the pump during crank? Does it have to be cranking or can the key just be turned to on?

Thanks!
 
It'll only have power for a couple seconds when you turn it to on - I don't believe it's powered while cranking, but not sure.

You can probe the ASD relay output at any one of the injectors - it's the pin with the dark green wire with the orange stripe going to it. Also, cranking it with an injector unplugged should probably trigger a CEL, so you can make sure the ECU is actually alive enough to notice an unplugged injector.

The fuel pump relay I believe feeds the dark green wire with a white stripe going to the fuel pump harness but it's been years since I checked, make sure that color code is right.
 
has to be cranking. at key on it will get a 2 second prime signal and shut off

disconnect the connector and attach the test light, and crank

or

jump 12 v into the feed wire at the fuel pump relay and then test for it at the fuel pump connector.
 
Good point, I didn't even think about that.
 
I watched this youtube video: http://www.youtube.com/watch?v=lLdsqXyj58g
Seems like it's worth a shot. What would jumping terminals 30 to 87 on the fuel pump relay tell me and rule out? It would allow me to listen to the fuel pump if it comes on. If I jump the pump relay and the the pump doesn't come on what would that tell me? Bad fuel pump or bad wires but could any grounds be bad and where?
 
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