WilliamAV

Hello Jeep enthusiasts. Perhaps you can lend some advice. I own a 98 Cherokee Sport 4.0 with automatic transmission and part time 4x4.

Recently the overdrive stopped working and the engine light came on. Manual shifting of gears worked okay. OD would work intermittently. Took it to the dealer and they diagnosed that the speed sensors needed replacing. They did the work and the problem was resolved for about three weeks.

Again, began experiencing intermittent failure with OD but manual shifting was okay. Check engine light came on but not at first. Returned to dealer and this time they said my Transmission Control Module needed replacing. I asked if they had checked all of the related wiring and they assured that they had. TCM is no longer made as an OEM part so I had to find one via salvage.

Had the dealer install the used TCM and program it. Good news, they are now receiving a signal from the TCM. Bad news, the problem is not fixed and they are now getting info that the solenoids are bad.

So they replace the solenoids and the problem is still not fixed. Now they are telling me that their support line is recommending that the entire valve body needs replacing. Oh, and the valve body is no longer made by the OEM.

I am dubious. Hence my post here.

I am not much of a mechanic, hence my reliance upon the dealership. However, it seems to me that everything thus far has been an electrical problem in nature. Would replacing the valve body likely make any difference here? Or would a better course of action be to replace all of the related wiring?

Obviously I am at a loss and I am not feeling very confident in the dealership right now.

Thoughts? Suggestions?

Thanks.

disguay

Sometimes automatic transmission failure can be resolved by actually disconnecting the TCM from the tranny. Try that and see what happens. With transmission work, I always just recommend replacing the whole unit in cherokees if anything goes wrong because you can pick up a whole transmission for about $200 and that will save you soooo many problems down the road because it's normally when one thing fails that other things will start to fail.

car5car

Demand your money back, file case in small claims court.

WilliamAV

If you disconnect the TCM permanently, will the automatic transmission still work? Or will you be left with only manual shifting?

As to replacing the entire transmission instead of doing it in pieces, would you be using an OEM transmission or an aftermarket build? And would you be replacing all of the related wiring as well?

disguay

First of all, i would demand my money back like car5car stated. You have been ripped off and screwed over. They "diagnosed" your car and that diagnosis states that their repairs will fix your problem. They are idiots, and you should get your money back.

As for disconnecting the TCM, I have never done it, but there was another member who was having tranny problems and they just disconnected the TCM all the way and it cleared up everything. I believe they just threw it in drive and it shifted through all the gears.

As for the tranny, I'm talking about going the OEM used route. The AW4 is bulletproof until you have one small problem in it. For instance, it will run to 400k miles easy with no hard feelings, but you overheat it once and the whole unit is toast. I've seen it happen more than once. For me, a used AW4 that goes forward and shifts through all the gears is just as good as a rebuilt or OEM unit. All the tranny units will fail due to misuse and not wear.

car5car

Here is what I would do:
get factory manual and aftermarket transmission manual.
Keep reading them until you understand how transmission works, particularly overdrive.
A lot of transmission problems can be repaired w/o removing transmission.
Overdrive unit on many transmissions can be removed and replaced w/o removing transmission. Most likely OD is run by solenoid, which can be $40 from dealer.

may pop

Torque convertor lock up turned on by a solenoid. If you disconnect the TCU which is under the dash above the drivers right foot. The trans should go through the gears if you shift manually starting in 1st gear. If you have all gears the mechanical parts of the trans are working. As you drive with the TCU hooked up at 50 MPH right foot on the gas tap the brakes with your left foot. The RPMs should rise 3-500 miles. This is controlled by the brake light switch. This tests the TC lock up. Ive changed TCUs and never had to program them. Just grab one at the junk yard and install. What codes are you getting?

Bowbowman

Hey WilliamAV I've had similar problems in my cherokee with the exact same year and specs as yours. I recently replaced the transmission speed sensor and the nuetral safety switch thinking that would do it, but nothing worked. When in overdrive, its like its trying to take of in 3rd gear or something, almost no acceleration at all but manually shifting into gears is fine. I'm definitely subscribing to this thread to see what people come up with to fix. Good luck!

Willys55

I know you (WilliamAV) said your not a mechanic, but before jumping down the throats of the Dealership Service Writter and Technician, have you considered taking it to a Transmission Repair Shop?

Have them check these 2 items......
1. Check for power on the Light Blue wire at the Torque Converter Control (TCC) and Overdrive (OD) solenoids at the left rear of the transmission electrical connector.

2. Check for a ground at the Violet/Yellow wire Powertrain Control Module (PCM) pin 54 for TCC and a ground at the Brown/Light Green wire pin 55 for OD control.

Also it should be noted that the TCC and the OD solenoids are easily plugged up with small debris from normal transmission friction plate wear, those fine particles cause sticking and slow responce. Any Idea as to when if ever the tranmission was flushed or had a fluid and filter change?

If it turns out that some of the repairs the dealer did were indeed not needed, then after having proof from the other shop you go and get your money back.

redmuck

mine wouldnt go into overdrive either,i found my tps was bad,so i changed it, now i have overdrive.

WilliamAV

Update: I got the jeep back from the dealership a little over a week ago and thus far no problems. Hopefully it stays that way.

Thanks to everyone who offered their advice.

Let me try to answer the outstanding questions:
1) Manual shifting has always worked fine including top gears so my understanding is that the torque converter was working fine. Didn't get to do the road test suggested as it was in the shop the whole time.

2) Before giving the go ahead on replacing the TCU I had the shop test all of the relevant electrical lines for voltage and ground. They reported that they tested okay.

3) After they replaced the solenoid the problem was still unresolved and they dealership was advised by the manufacturer to change out the valve body. The dealership located a used valve body and installed it but the problem remained. (Sidebar: myself, the service manager, and the shop foreman had all been skeptical that this would solve the problem.) So, back to the drawing board.

4) Before reinstalling the original valve body, it was determined that the part was dirty (and perhaps clogged) so it was reconditioned (ie. cleaned) and then returned to the transmission. Somehow that did the trick and now its working again.

5) I've never overheated the transmission and it had been serviced about seven thousand miles prior. Other than routine service the tranny has had no other work and I've never had a problem with it before. Total Mileage is 170k+

6) Wasn't trying to bash the dealership unfairly. I've been doing business with this particular location for five years and my jeep has always been serviced by a dealership or myself (using mopar parts), with the exception of tires. I spend a lot of money with them and am generally very patient but the customer service was a bit lacking this time. All told they had the jeep for about five weeks over a two month period. So, yeah, I was very patient. They had already charged me for replacing the speed sensors. The second time, they only charged my for replacing the solenoid. And they gave me a big discount on my rental, but all told, it still cost me around 1,500 for the two jobs including rental fees. I don't think they made any money on this job given all the hours they spent on it, but that is their problem.

7) I spoke at length to a local jeep mechanic and he pointed me to a couple of local transmission shops that have extensive experience with the AT4 should I have problems in the future. Thanks again and good luck to anybody having problems with their OD.

SweetLou

Neutral Safety Switch can also cause the jeep not to go into OD.