95 Jeep Grand Cherokee not shifting into overdrive

[tinker1121]

I have a 94 GC with 83,000 miles and three garages cannot determine the problem. Noticed last summer that the overdrive acted up and not shifted when traveling over hilly terrain. I drive mostly in town so didn't notice much except that sometimes it seemed to stick in gear.

Last week it was doing it almost daily and downshifted into first while I was on the highway doing 45. I was just about to the mall I was driving to and made it and it was fine when I got back in it to drive home.

Cottman was clueless and said not a module but for $400 they would "take the transmission apart" and I said no thanks.

I have been told NOT to flush the transmission as it could cause more problems.

Has anyone made any progress? I guess my next step is to take it to the dealership which I am trying to avoid a huge repair bill or trade the thing in.

[ofnobledescent]

Please read my earlier post on this subject (Not on this thread but my own problem thread). Turns out it was was the convertor.

[viking55]

Originally Posted by viking55

I called the transmission shop and they told me it would cost $300 to change the thermostat and also thought I was crazy getting my information from the internet. The TCM is only $200 so I'm still waiting on it. I just don't know what to do anymore. In the meantime, the JGC is still starting in 2nd or 3rd and at the end of the day it is fine.

thanks for letting me know how much the t-stat costs. I am not a mechanic. I've been too busy to pursue the problem lately. I need to find a new mechanic thats for sure.

[Oregon94Jeep]

I had the same problems with my 94GC not shifting into overdrive, except my whole trani went out after one day of this. The intermediate shaft and a plate sheared off, probably due to not getting enough fluid in that area. Anyway, a friend and I rebuilt the trani and got it all back together(major pain in the butt) and in but I am still having the overdrive problem. I disconnected one of the hoses while it was running to make sure that the fluid was being circulated properly and it was pumping away. I feel confident that we installed everything correctly, anyone have any idea why the overdrive issue? I have heard someone say it was their catalyitc converter and another that it was their thermostat. To me, that doesn't seem relevant to the transmisson. I think those problems were most likely keeping the engine from functioning properly, and not shifting into overdrive was a result of the engine, not the other way around. Anyone have any ideas?

[Midasgirl]

Originally Posted by Oregon94Jeep

I had the same problems with my 94GC not shifting into overdrive, except my whole trani went out after one day of this. The intermediate shaft and a plate sheared off, probably due to not getting enough fluid in that area. Anyway, a friend and I rebuilt the trani and got it all back together(major pain in the butt) and in but I am still having the overdrive problem. I disconnected one of the hoses while it was running to make sure that the fluid was being circulated properly and it was pumping away. I feel confident that we installed everything correctly, anyone have any idea why the overdrive issue? I have heard someone say it was their catalyitc converter and another that it was their thermostat. To me, that doesn't seem relevant to the transmisson. I think those problems were most likely keeping the engine from functioning properly, and not shifting into overdrive was a result of the engine, not the other way around. Anyone have any ideas?

Once it warms up, does it shift into overdrive at all? I have a hard time believing that it is the converter. And, if it does shift eventually, I think it is a pretty cheap and easy fix to replace the thermostat. I have had two Jeep GC and this has fixed this problem both times. However, I am having to change the thermostat every second year.

[Oregon94Jeep]

Originally Posted by Midasgirl

Once it warms up, does it shift into overdrive at all? I have a hard time believing that it is the converter. And, if it does shift eventually, I think it is a pretty cheap and easy fix to replace the thermostat. I have had two Jeep GC and this has fixed this problem both times. However, I am having to change the thermostat every second year.

I don't know midasgirl. It's not overheating or anything so I don't think it's the thermostat. I replaced the radiator and fan just a couple years ago and everything's cool.

[94limited8silly]

im having the same exact problem... im going to try the thermostat swap and see what happens... also i know my temperature sensor on the thermostat rusted off and does not read.. so im changing that... hopefully thermostat fixes it

[Cobradon]

I experienced the same problem off & on over the last 2 years. I used to sit and let it warm up until the thermostat opened, then shut it off and restart to get all gears. That got time consuming quick. Tranny fluid was dirty. Had the tranny flushed and tranny conditioner added to the ATF+4 tranny fluid (do not use any other type). Since then it only happened a few times when it was rather cool outside. tranny temperature sensor may be faulty even though no code 16 came up. Cooler weather is approaching and I'll be monitoring the shifting. If it continues to be a problem, I'll change the tranny temp sensor. Can't say if this is the general solution but it is working for me right now.
FYI
The transmission temperature sensor is mounted on the overdrive/torque converter clutch solenoid assembly and provides input to the TCM. When the temperature sensor reports 30 degrees F or colder, there will be no overdrive.

[fredjacksonsan]

If the ATF is too cold, the trans won't shift into O/D either, until it has warmed up. IMO it could be the thermostat, but could also be the ATF fluid temp isn't being sensed correctly.

[trannyman52]

you might look into installing a transgo or superior shift kit ,,,resolves many shift issues with these transmissions !!!!!!!

[fredjacksonsan]

Any results? I am figuring that the shops you've taken it to have already checked the fluid level.

[Andym90]

I believe to have found the problem to the locking out OD problem seems to only happen when engine gets warmed up but I noticed if I apply light pressure to the break while cruising transmission shifts into OD and stays ther as long as pressure is applied to brake. As soon as I let off the brake transition slips back into 3rd. Have repeated this many times over with the same consistent results so taking it to an auto electrician hopefully can get this problem fixed

[Cabbie1]

Andym90 I am curious to know what you find out. It's great to see a recent post on this issue, as I am currently experiencing it myself. I'm going to go try your break pedal suggestion, I let you know what happens on my end.