95 GC Transmission Issues

[ktcakes]

First, I admit that I am only a girl. I have a 1995 Grand Cherokee with 150K miles. The initial problem was that sporadically, the O/D Off light would come on upon starting the vehicle and the vehicle would not shift above or below second gear. Pressing the O/D button would not make the light go out. I had the Auto Tech teacher at school look at it and he said there was a lot of metal in the pan and recommended a transmission shop. I didn't want to spend the money, so I drove the vehicle short distances for a couple months until I got up enough nerve to spend the money. I found that recranking the vehicle would clear up the shifting and O/D light problems. The transmission shop tech told me that it could be a bad sensor, but since there was a lot of metal, the transmission probably needed to be rebuilt anyway. Well, I have a rebuilt transmission now and the O/D Off light still comes on sporadically and the vehicle will shift between second and third, but that's it... Unless I manually shift it into First. Then it will not shift into Second if I manually shift to Second, but it will if I shift into Drive. I've taken it back to the shop once already. I drove it in while it was malfunctioning so that they could test drive it and see the problem for themselves. They have read the codes and said that the transmission was not getting enough power, but they have been unable to isolate a short or bad connection anywhere. The sensors all check out fine. Is there something else that might be going on?

[ktcakes]

I am posting just to bump up my inquiry. I mean no offense to others who are posting with their own concerns. Surely, someone has a solution other than an exorcism or pushing my vehicle into a deep ravine.

[legartner]

Hey Cakes, I was just getting ready to post the same problem I am having with my 95GC. You've described the very problem I'm having with the O/D light coming on. I can clear the light by shutting down the engine and restarting, but sometimes I have to do it several times. I also can shift gears manually, but the trans seems to stay locked into a high gear when the light is on and won't shift down when going up hill. Once the light goes off it shifts properly. Am I on the same track as you?? If so, I will be watching intently for someone to post a fix. Thanks, and good luck and girls have problems too!

[ktcakes]

Yes, your problem is exactly the same. The transmission tech who has been trying to isolate the problem is on vacation this week. My vehicle will be going back in the shop next week. I will keep you posted on any developments. Hold off on getting a new transmission! I suspect that was not the initial problem.

[dsshunter]

I had a problem recently that was in this same area, but mine was with a 93 GC Limited. After having some work done on the heater coil, I picked up the vehicle and found that the transmission was locked in 3rd gear. The shop that fixed it couldn't find the problem so I contacted a specialist on Jeeps. He informed me that the transmission lockup was a protective measure built into their transmissions to protect them from damage. He told me to check the TCU (Transmission Control Unit) fuses in the Main fuse box under the hood. It was one of the mini fuses in front, third from left (facing front of vehicle). One is a 10 amp (Battery feed), and the one below it is a 15 amp (Ignition Feed). Both of these control power to the transmission. If these are good it might be the Transmission control module itself going bad. Try checking these and good luck.

[hastreiter]

I have the same problem. Replaced the trans temperature sensor and checked the electrical harness. no luck

[hastreiter]

I thinik that this has to be an electrical problem in the TCU or the computer brain. Have you solved the problem yet?

Originally Posted by ktcakes

First, I admit that I am only a girl. I have a 1995 Grand Cherokee with 150K miles. The initial problem was that sporadically, the O/D Off light would come on upon starting the vehicle and the vehicle would not shift above or below second gear. Pressing the O/D button would not make the light go out. I had the Auto Tech teacher at school look at it and he said there was a lot of metal in the pan and recommended a transmission shop. I didn't want to spend the money, so I drove the vehicle short distances for a couple months until I got up enough nerve to spend the money. I found that recranking the vehicle would clear up the shifting and O/D light problems. The transmission shop tech told me that it could be a bad sensor, but since there was a lot of metal, the transmission probably needed to be rebuilt anyway. Well, I have a rebuilt transmission now and the O/D Off light still comes on sporadically and the vehicle will shift between second and third, but that's it... Unless I manually shift it into First. Then it will not shift into Second if I manually shift to Second, but it will if I shift into Drive. I've taken it back to the shop once already. I drove it in while it was malfunctioning so that they could test drive it and see the problem for themselves. They have read the codes and said that the transmission was not getting enough power, but they have been unable to isolate a short or bad connection anywhere. The sensors all check out fine. Is there something else that might be going on?

[hastreiter]

WHat does your tech friend think about replacing the computer brain or TCU.

[dsshunter]

Sorry, my problem never went past the fuses. the 10 amp fuse was blown and was a simple fix. This is a good starting point, and if they're OK you might want to move on to the TCU voltage supply and then the TCU itself if needed. Good Luck

[ktcakes]

I have had some scheduling problems with getting my vehicle in the shop this week. I will let you know what is found. I dread it as I have spent way more than I wanted to spend on the repair and I suspect it is more than I should have spent... Live and learn, I s'pose...

[hastreiter]

Here is a reply to my posting on Car talk.

The VSS (vehicle speed sensor) could be sending the wrong signal to the computer. When cold, the sensor could be telling the computer the vehicle is travelling too slow to shift up. Then, when the engine is up to operating temp you stop and turn the key off, then back on, thereby resetting the computer.
Hey, just a guess.

Post Extras:
transman618
Overly Enthusiastic Enthusiast



Reged: 12/06/03
Posts: 315
Loc: Lithia Springs, GA
Re: 95 grand Cherokee OD/ passing gear locked out
#229347 - 08/11/04 11:02 PM Edit Reply Quote



Why dont you take it to a transmission shop and let them scan it ???

[hastreiter]

Via the internet I found some more possible solutions. Pleaaase provide feed back;

Trans oil Cooler - Not a fix
Speed sensor - not a fix
Temperture sensor - not a fix
Fuse - not a fix
electronic shft control - not ruled out
overdrive modual - not ruled out
2 Solenoids by tranny - possible fix
Overdrive switch itself _ not ruled out
Short in the harness by the fire wall

[ktcakes]

I will definitely keep you posted. I will be dropping it off Monday. The scan code says that the transmission is not getting enough power. They have tried to isolate a short, but have not found one anywhere...

[hastreiter]

An email rely to my car talk question advised that if it is a short it would be in the harness by the fire wall, or where the ac line crosses the harness ( short do to excess moisture), or at the sol pack.

I do not understand why a mechanic can not solve the problem or problems by Q &A.

1. When the engine is cool, Why does the Trans mission strart off in 2nd or 3rd gear?

2. Once the vehicle is approaching 40mph in this condition why doesnt the over drive kick in?

3. At 45mph and the gas pedel is floored why is there no passing gear?

[hastreiter]

KTCakes
Any luck?