Jeep 42RE transmission slipping, but improving

[Jonathan Stiver]

Yesterday I bought another Grand Cherokee, this ones a 2000 4.0L RWD with 271k miles for $600. I bought it because the body and interior are quite clean and nice, and the A/C works. That’s about all it has going for it. Well it still runs at least. Anyways, it was advertised as having a bad transmission and I already had another one for it just sitting around.

When I test drove the Jeep, it definitely had all kinds of transmission problems. The fluid was grey/black but didn’t smell too bad like most bad transmissions I’ve come across. Well, after towing it home I changed the ATF & filter for the hell of it. There wasn’t an unusual amount of particulate matter, it was more just like gunk. So I cleaned what I could and gave it a shot with new fluid. Instantly a 90% improvement. Engages gear right away, solid in reverse, 1st, and most of 2nd, but starts slipping/shaking a little sometimes when warmed up and has trouble shifting 2-3 sometimes.

Now I’m thinking this thing might be salvageable, but I’m not sure what to do next. I’ve heard of people using certain additives in situations like this, even with this specific transmission, and having good results. I would even be game for trying to adjust bands or cleaning up solenoids and stuff. I’ve got nothing to lose, whether it holds up for a week or a year I’ve already got a known good replacement sitting on the floor. Would be open to any suggestions! Thanks!

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[Rudy Wilmoth]

🙂 You do not want to use any of the transmission repair in a bottle to try and fix this vehicle. I would suggest you find a good transmission shop and let them do a transmission flush. When you changed your fluid and filter, you did a good job, but you only changed around 40% of your total transmission fluid. An transmission flush will completely change your transmission fluid and may help degunk your transmission. Now you do have over 200,000 miles on this vehicle, this will make it a better vehicle, but you may end up getting the transmission rebuilt or replaced when all this is said and done. Good Luck.

[Jonathan Stiver]

Thanks, but I barely even want to spend the cost of the ATF on this experiment since I have a much lower mileage replacement transmission already on hand. I figure most products do more harm than good, but I was surprised by some StopLeak on another car last year so who knows. One thing I considered was SeaFoam makes a formulation for flushing out transmissions. I’m just guessing but I think all the passages and solenoids and what not are clogging up in this vehicle. Maybe if I run the ATF SeaFoam for a few days then flush and fill a few more times there is hope for this very old transmission.

[EricTheCarGuy]

A friend of mine had a similar issue with his Grand Cherokee. He installed a trans cooler and hasn’t had any problems since. Even if it does fail, you can still run the cooler to prolong the life of your replacement trans. Good luck and keep us posted.

[Jonathan Stiver]

That’s a great suggestion, thanks Eric. I was starting to wonder if the factory cooler lines or radiator were clogged. It’s worth noting my friends 04 has a separate cooler from the factory. I was going to try flushing it like you did before replacing your Odysseys transmission. But I think I’ll install an aftermarket cooler and temp gauge and see how it goes.

[Jonathan Stiver]

UPDATE: Changed the fluid again once it mixed in and turned brown. Shifting improved some but there was a new noise. Added half a bottle of SeaFoam Trans Tune, shifting greatly improved, pretty much normal, but the new grinding noise got louder. Added 1/4 bottle of Lucas Trans Fix, shifting deteriorated, pump noise increased, grinding noise decreased. About 50 miles later the grinding noise became unbearable at nearly any speed, particularly decelerating / downhill but would disappear when coasting in neutral. This baby is toast. I should have it pulled and dissected this weekend. I guess it was still worth it all as an experiment. Since it was shifting better, maybe this one is rebuildable.

[EricTheCarGuy]

It was worth a try. At least now you know. Thanks for the updates. Let us know what you decide to do to repair the problem.

[Jonathan Stiver]

Since I’m moving to a non-emissions inspection county later this year, I’m going to convert the car to OBD-I and use an AW-4 transmission the Cherokee uses that has a much better reliability track record than Chrysler’s 42RE. I found a guy selling pretty much a complete conversion package – transmission, transfer case, torque converter, NSS, CPS, kickdown cable, wiring harness, and PCM for only $250. I’ll easily be able to sell my other 42RE that is in NY for $300-600 in the spring and could net a great Jeep for under $500.

I may still try to repair the old transmission for fun/spare for my other WJ/resale. I’ve successfully dissembled a Prelude manual transmission to have the 5th gear swapped/pressed (for an Accord EX 5th for lower RPM highway cruising 😉 ) and got it back together fine but I’ve never tried to mess with an auto… Will post a couple pics of old trans in a few days.

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