Tranny Problem

Hey Guys,
I am inheriting a 97 Cherokee Sport 4.0L. The Jeep is in Great condition except that the transmission has a problem. It shifts very smoothly until about 50 MPH and then it goes inbetween 3rd and 4th gear wildly this also happens when going up inclines 35 degrees or higher. The check engine light goes on and off at will and the car doesn't have this problem until its warmed up. I have no idea what to do any ideas?

Thanks

Doesn't sound very pleasant... Have you tried locking it down into 3rd gear when this starts happening?

Sounds like a faulty tps, and doesn't sounds like the tranny is at fault.

You say it also does this on hillclimbs? 35 degrees is steeper than most driveways ive ever seen, and i've never seen a highway steeper than 8 degrees, so i'm assuming it also shifts between 1-2 or 2-3 randomly?

List the mileage too, that usually helps us determine the true issue.

Well I live on the top of a mountain and its about 2 miles up from the base which is 2 miles up that my car goes on several hills 35 degrees about or more mabye a little less. Anyway it shifts smoothly between 1 and 2 and 2 and 3 but not 3 and 4. Its 177k miles never had the tranny replaced and is very well kept also its an AT I dont think i mentioned that before.

Do you ever try to lock the transmission down into the "3" position?

That should keep it from even trying to shift to 4th..

And you don't need 4th unless you're doing 55+ regularly..

Mine never leaves 3rd, because I don't let it.

Sorry, I missed that the first time I do and that stops it from slipping or anything like that but to get to school I have to travel on an interstate and the speed limit is 65 so i do travel at 55 or above regularly. But putting it in the 3rd position it doesnt shift which is what I do when going up hills.

Take it to the parts store and have them run a scan on it.... It'll throw codes if the CEL is blinking.

First thing I would do is see what kind of trouble code(s) is/are being generated.....that might help narrow your search. Just because the light goes out doesn't mean there are not any codes stored.

What does the fluid look like? Is it at the correct level? ATF over time will turn a darker color (vs it's bright pink color when new).....the color doesn't mean it's gone bad. Smell it; if it has a "burned" oder to it then you may have some internal problems best diagnosed by pro. In any case, its probably wise to change the fluid....once you've determined your problem.

Check the adjustment of the transmission valve cable (TV cable). This is a heavy cable connected to the throttle body on the radiator side (it looks like the cruise control cable if your Jeep has this). My '00 has a metal tab in a plastic mount; you push the tab in with a flat blade screw driver to release the adjuster while at the same time pulling the cable out (which would be toward the passenger side of the car). Once it's fully extended, get in and "floor" the accelerator; this will ratchet the adjuster to the correct position. This is *not* a "kick down" cable; it does a lot more and if it's out of wack can cause some shifting problems.

Does the transmission lock up in 4th? What you might be experiencing is the lockup clutch cycling between a lock and unlock condition. It should lock up in 3rd if you place the transmission in the "3" position (you should be able to feel it as an additional shift).

Here's a long shot: Pull the throttle body and scour it clean....get all the carbon and crud off the surfaces and clean out the vacuum hole in the venturi and the idle air bypass passage. The tranny computer may be getting an incorrect vacuum input from the TB causing it the grief your having. The tranny in my '00 Sport suffered strange shift functions when I put a bored TB in place of the stock unit....only thing that fixed it was swapping in the original TB....vac signal to trans computer was messed up.

Went to the auto store this morning and It says

ENG: 42/------
Fuel Level Voltage
HI

I found out also this morning that the fluids and what not where replaced no more then 300 miles ago or about 2 weeks ago. So thats what im dealing with.

The AW4 tranmission is electronically controlled, so I doubt this is a mechanical problem. Most likely, you have a bad TPS sensor which is a common problem.

If you can, you might want to verify that they used DexronIII in the tranny. Many shops, including the dealer, incorrectly assume this is a Chrysler tranmission and put in ATF4+ which is the wrong fluid and can cause tranmission slipping.

I would definitely check the adjustment of the TV cable. On lite/normal acceleration on flat road it should shift into OD at 45mph (give or take a mph or two).

Well it does try to shift into OD at about 47 and or so in my experience but then it downshifts back into 3rd and then trys again and its an endless cycle of that.

Also how would I go about checking the TPS?

scoobyxj said:

I would definitely check the adjustment of the TV cable. On lite/normal acceleration on flat road it should shift into OD at 45mph (give or take a mph or two).

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Do check the throttle cable as it's easy to check and if it's way out of adjustment it can cause shifting problems. It won't affect the shift points though as it's an electronically controlled trans. I agree with the previous posts about a bad TPS since it's a pretty common problem.

Alright well I will do both of those tommorow but I am going to bed cause its about 6 am. Happy Easter everyone.

I checked the Throttle cable and it did need some adjusting but it didnt solve the problem. I am seriously considering buying a new TPS.