Hi Jeepers. I'm having a problem and wondered if anyone has had a similar issue.

I have a 1996 Cherokee SE 4.0 with four wheel drive. I've had it for about 7 months, it has just under 149k miles. It's my daily driver. I've never had an issue with her until last week. I ALWAYS let her warm up before driving, usually 5-8 minutes or until I get a good chunk of space on the coolant temp gauge. It drives perfectly when not quite up to operating temps, but when it starts to warm up and drives for about 10 minutes, my transmission will start to miss shifts. It won't ever slip when I give it gas, but it will rev up past 3000 before it will shift, and usually I have to let off the throttle before it will shift. Sometimes it will run normally and then miss 2nd entirely and go into 3rd or "limp mode", again shifting smoothly into 3rd and returning to first when i stop, but not shifting out of 3rd while driving. When working correctly otherwise, it shifts buttery smooth and right on time. No loss of power noticeable. I have no ECU codes and no leaks that I can find. No noises from the tranny whatsoever. Trans fluid is still red, maybe a little milky, and smells slightly burnt but I've smelled much worse trans fluid before on a trans that still ran fine. I think it's probably 100k mile fluid.

This Jeep was a city government car and then owned by someone who probably used it to haul trailers on the weekends. The engine is easily the best sounding 4.0 I've ever heard and the body is nearly rust free (I live in rainy Washington... unheard of here!). I'm worried my luck has run out and my tranny might be going bye bye, but only when hot??? And all in one day???

I've read that a bad TPS solenoid can cause these types of issues, since it shifts fine normally but once the solenoid gets hot the wires expand and find a short, or something along those lines. Since it doesn't slip or shake otherwise, I'm confident my issue is electrical or sensor related. The problem arose suddenly one day while driving around town, on the way back home I noticed it miss 2nd and go into limp mode 3rd. I know a trans flush will do more harm than good at this point in it's life, but I may need a drain n fill. Could my bands need to be adjusted? Maybe they get hot and expand, loosening further and throwing off the computer? If I had a coolant line blockage, would it cause a leak or simply back up into the reservoir? Also wouldn't the ECU get a code for an overheating trans? I'm not an expert as you can tell, lol. Just a Jeep lover who wants to make his baby all better. If you need any more info let me know. I have the day off today so I will by checking back often.


Thanks,
James

 

Forgot to mention, there is a small weird noise when driving. It gets louder when I turn, but it's not always there. It sounds like quick knocking coming from the from right axle, but it could just be echoing and actually coming from under the car. It's not an engine knock obviously. It sounds like there is something spinning and rapping against something else as it gets faster as my wheels speed up. Maybe my flexplate bolts have backed out and are rapping against the case? Can that happen? I'm going to check the flexplate bolts and report back. Doesn't seem like that can cause my problem but can't hurt to ease my worry.

 

If the fluid smells burnt, even just a little, its best to replace it. What do you mean by 'milky'? What does the coolant look like? If the transmission lines are connected to the radiator, a leak is possible, mixing coolant and transmission fluid.

Not sure on the noise. My best guess is the wheel bearing or u-joint. Balljoint, even. Lots of moving parts up there.

 

Thanks for the tips. After much reading, it was narrowed down to be the throttle position sensor. Those things can cause some WEIRD issues in Jeeps that will never throw a code! Went ahead and changed my tranny fluid anyway. Fluid was red but more on the dull brown side, probably 30,000 mile trans oil. Adjusted the kickdown cable too. Runs and shifts better than ever since buying it in August, shifts smoothly just under 2000 RPM. If you have any acceleration or shifting issues, I would test or replace the TPS first before trying anything else. Turns out they like to fail gradually, causing major running problems while tricking the ECU into thinking it's fine. They can also fail and cause issues you may not notice, like running lean or rich. $40 to have her running like smooth butter. Don't settle for a Chinese sensor either!!!

Cheers,
James

 

PS. In my original post I referred to a "TPS solenoid" but I meant the TPS sensor. Wasn't familiar with the electrics in that part of the motor yet. Happy Jeeping!

 

One change isn't enough. Do it again in a thousand miles, then another, then another. Or see my sig to get it all cleaned out.

 

Great advice^^here.

 

Thanks, that's my plan. I made the mistake of topping it off with ATF+4 before I changed it, as it was a bit low and there is a lot of conflicting information on here about trans oils. I drained and refilled with Castrol Dex/Merc like i should but I've read some snippets on here about "jelling" occuring when mixing Dexron and ATF+4. I only added about 1/3 of a quart of ATF+4 and drove it enough to mix in well, then drained it two days later. I know the torque converter holds about 3 quarts. Sticking with Dex/Merc from now on. No way to know what fluid was used before but the Jeep was a city government vehicle, so clues point to ATF+4 being used later as per the service bulletin. I know changing oil type on old engines can be stressful, but reading how the AW4 can have slippage issues with ATF+4, I went with the lesser of two evils and used the Dex/Merc. Should I be okay until my next trans oil change? Or should I drain and fill at more like 500 miles to be sure I'm running Dex?

Thanks all,
James

 

I'd flush it. Either with short interval drain & fill, or the method outlined in my sig. Wun er tother!