Jeep TJ auto

[Northwest Wanderer]

Has anyone has any reliability issues with the 03-06 TJ auto. I belive it is the 42rle, mine has been giving me grief and I am trying to get it fixed before next spring. (If not applicable here just tell me and I'll post it to where it is)

 

[smritte]

yes, its a 42RLE

I was fairly amazed how poorly mine was engineered in my 04. First and foremost is the way they geared it. The over drive is too tall. they did this to try to raise the mileage a bit for the fuel standards. To keep the engine from bogging, they slip the converter more. This creates a bunch of heat. Your trans should be running at or lower than your engine temp. Mine with 33" tires ran in the 250-260 range and hit 300 pulling hills. anything over 250 is hard on the trans and anything over 275 spells death. When I went to 35's it was way worse. 350 was not unusual. I added a large cooler and fan under the rear of the vehicle and another in the front. That's what it took to get the temps down to acceptable levels. I added a temp gauge after reading similar issues on different forums. I wasn't the only one with this.
The other issue is the shift pattern. Someone makes an inline tuner that fix's this. I don't remember who. Some of my friends ran it and it made a big difference. One of the guys at work was a Chrysler/jeep tech. he had told me it wasn't unusual for those trans to come in burned up at 50-70k miles.

 

[Northwest Wanderer]

This level or reliability is making me wish I didn't sell my YJ for a Rubicon. I'll look into seeing if I can make it more robust or ill find a manual Rubicon if possible. Thanks for the info

 

[smritte]

Put a big cooler on it and call it good. This is the gauge I ran Deraile. This is the remote cooler. The one I added in the front was from them also but I don't remember which. I just accepted the shifting. If you haven't changed the fuel injectors to the 4 hole, that's something you need to do also. Huge difference.
I had bought my TJ because I wanted that wheel base and I was tired of having to reengineer my older jeeps. When I was done debugging it, it worked well for the most part. Again with the "reengineering".
The "go around" for the trans issue is (was) grab the trans and trans computer out of the same year cherokee. Grab a manual trans engine computer out of a TJ. It all drops in. The trans computer will not talk to the engine computer and runs in default mode. In default, it still runs cooler and better. One of the guys in my Jeep club did this and it worked great. It wasn't worth the several thousand to me though.
I sold my TJ Rubicon last year. It had 48k miles.

 

[Northwest Wanderer]

I'll look into the cooler I've been told I have to regear my 4.10s to 5.31 to just run 33s with the auto. I'll do more research to make sure. I'm just worried about it downshifting or going into limp mode at 80 to 85 mph (MT speed limit). Its given me a lot to think about.

 

[Downs]

The "go around" for the trans issue is (was) grab the trans and trans computer out of the same year cherokee. Grab a manual trans engine computer out of a TJ. It all drops in. The trans computer will not talk to the engine computer and runs in default mode. In default, it still runs cooler and better. One of the guys in my Jeep club did this and it worked great. It wasn't worth the several thousand to me though.
I sold my TJ Rubicon last year. It had 48k miles.

Do you mean Grand Cherokee? No XJs had the 42RLE. They all ran AW4s. Which from my understanding has become quite the popular swap for TJ drivers.

 

[smritte]

Do you mean Grand Cherokee?

You may be right. I dont remember where the trans came from they used. I do know the drive line was the same. I-6 and bolted to the transfercase. I do know the trans had a different designator (part number) and it had analog sensors which is why you had to swap the computer also.

 

[smritte]

I'll look into the cooler I've been told I have to regear my 4.10s to 5.31

4.88's are a better choice. I didnt like how small the pinion got with 5.13's. I ran 4.88 up to a 37" tire. my street tires were 33's and it was a good balance street driving.

 

[Northwest Wanderer]

Sounds like i should be ok with 33s on my tj with the 4.1 from the rubicon

 

[smritte]

You will be fine with 4.10 and 33's unless you start doing hard trail's. I ran the Rubicon with mine before I started modding it. The only issue with bigger tires is trans cooling.

 

[Northwest Wanderer]

I'll install the cooler and go from there.

 

[LJ Rob]

The Derale transmission cooler kit helped cool mine down.
I believe the factory thermostat in the kit will turn the fan on at 180 and off at 160-165. Thermostat switches can be found if you want to change the on/off temps to something else.

The transmission's 30-something percent overdrive is bonkers, especially since the torque converter is so small. Those clutches get whipped. Watch for a shudder on TQ lock-up to indicate the converter is beginning to go sideways.

 

[Autism Family Travels]

Sounds like i should be ok with 33s on my tj with the 4.1 from the rubicon

Yes, you will be fine with 33's on the rubi with 4.1. People have a weird obession with massively overgearing their rigs. they drive on the highway with the engine spinning at 3500 rpm or more all the time. DUMB!