95 GC Transmission Issues

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?

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.

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!

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.

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.

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

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


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?

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

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

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...

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 ???

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

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...

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?

KTCakes
Any luck?

I hope so! I picked up my vehicle about an hour ago. The technician told me that there was power going into the "transmission computer," but none coming out, so he replaced the wire. He started it up this morning and the same problem was there. He said that they replaced the transmission computer and it seems to be better. I have noticed that it is shifting more smoothly. After I had the transmission rebuilt, shifting seemed very abrupt. Is the "transmission computer" the same as a TCU? The tech wasn't condescending to me, but I think he tried to explain it simply. If this fixes my problem, it was a VERY expensive lesson to learn. I'm not sure how much this repair costs, as I was not charged for it. I guess I got a freebie. That was sarcasm, there. ;-) Good luck to you and I hope all it takes for your vehicle is a new "transmission computer!"

Please give us an update in a few days and thank you for the information! I know that this has been a frustrating problem.

Well, all seems well so far. Yesterday, I took a little trip to a town almost two hours away. I got there and back with no trouble... or speeding tickets! ;-)

What did they charge you to replace the TCM/TCU?

They only charged me for the rebuilt transmission, which was a little over $1900. I was told by someone that the TCM is not a very expensive part, but the installation can be expensive (around $200). So, I probably paid over six times what I should have paid to fix the problem.

P.S. LOVE your avatar!

Thanks for the info! I have been trying to locate a TCM, but most parts houses don't have them. I think you may be backwards on the cost, though...I think the TCM will cost somewhere in the $100 - $300 range, but only takes about 5 minutes to install, as it is easily accessible under the dash above the brake pedal, so installation cost should be minimal. However, I don't know where to get a TCM or what a good cost estimate should be. Anyone have any ideas? Glad yours is running fine now, even though it wasn't a cheap fix! :(

It's quite possible I have the prices reversed. I haven't delved too deeply into the pricing just yet, as I will give my vehicle a few more days before I am convinced it's fixed for good. I may be unsuccessful, but I believe I am due at least a partial refund since the transmission was not the problem, nor did it ever slip or act up in any other way. You may have to visit your dealership for the part. That's always fun! ;-)

I am having my transmission computer replaced this Friday. ktcakes have you had any problems?

I have had a little sputtering when I put it in gear after starting the engine, but that may be unrelated. So far, no transmission problems. Let me know how yours turns out and how much it cost you. I hope it fixes your problem!

ShadMan and hastreiter: Any luck with your new tranny 'puters?

Sorry, I posted this on another thread here, but forgot about this thread!

RESOLUTION!!

Well, I discovered that the sensor I replaced the first time was actually the Vehicle Speed Sensor (VSS) and not the Output Speed Sensor (OSS). I dropped the pan, changed the filter, replaced the OSS, added a few quarts of ATF+3, then flushed the tranny by disconnecting the transmission return line and draining into a bucket while adding new ATF+3 fluid until I noticed a difference in the color of the fluid. I wanted to make sure I completely drained the old fluid out (including torque converter, cooler, etc.) in case the previous owner had used Dexron/Mercron III. Filled to the proper level and test drove. No more erradic shifting!! I don't know if it was the fluid or the sensor, but I would definitely lean toward the sensor. $50 including fluid, filter, sensor, gasket. Sweet!

I was so excited I went ahead and replaced the front rotors and pads! ;) Tomorrow will be fluid drain/fill on the differentials, checking motor compression, changing spark plugs, andmaybe flushing coolant system if I get really bored!

Thanks for the help and suggestions. Upcoming projects are rear drum/disc swap, FIPK, headers (anyone know where I can get them cheap??), and maybe a lift (front-->rear coil spring swap), larger tires, and ring/pinion swap to 3.73 (or possibly 4.11). Keep the suggestions coming! :D

That's GREAT news! I'm very happy for you, but there is a part of me that says, "Grrrrrrr! Why did HE have to be the lucky one?!" Good luck with your projects! It sounds like you are going to be very busy!

LOL! :D Don't be a hater! ;)

LOL! I got nuthin' but love!

;) :D

I am having my transmission computer replaced this Friday. ktcakes have you had any problems?
Any luck?

I am still problem-free...

My Jeep is in the body shop. A kid in a pick up backed out of a parking spot and hit me. I will have to wait a couple of weeks to install the TCU

It is funny how we all have the same problem. I went to cottmans transmission with the same symptoms as all of you. they charged me 85 dollars to replace a relay that was not it. they told me that it was an electrical problem and to go in on the following day to service the transmission to further diagnose, thats another 65 dollars. well i never did go back. since i have a background in electronics i thought that i could give it a shot and i found the problem! the problem is in the TCM a small metal case by the left foot of the transmission. there is a relay inside that fails and makes it go into shutdown. The thing is that there is an eeprom that needs to be programed by a certified tech if indeed you need to replace it. well to avoid any further costs i bypassed the relay just by placing a simple jumper and guess what it works. well i have driving my vehicle for two weeks with out any problems. I need to replace the relay since that is not a permanent fix. i guess i saved about 300 dollars. email me if you have any questions and i will be more than glad to help.

Do you have to open the TCM to do the bypass. Please give us non-mechanical people some more detail on how to do this bypass and if the TCM is readily accessable. I can't find it.

Thank you so much!

yes the tcm needs to be opened. the tcm is under the dash board on the left upper part of the firewall. it has an orange conector. to remove tcm from firewall you need to remove 2 nuts acessible from the engine compartment under the hood. i will take pictures and send them to you if you request.

I am still problem-free...
Hey Cakes, sorry to take so long to reply, wife's been ill. I finally got around to checking the TCM. I was lucky enough to find one at a local salvage yard, ($19.00), I installed it myself, (two bolts and plug the cable in), then started the engine. I've been problem-free for almost three weeks now. I didn't have to have the TCM re-programmed and didn't have any other problems. Of course I'm waiting with held-breath for something to happen, but if not, I got off real cheap. Just wanted you to know how it came out and to thank you for your assist.

(P.S.) I would advise everone to change the TCM first when experiencing the same probles).

KTCakes
Any luck?
I have a 1995 Gc Limited Orvis. Love it . But it has the same problem with the od light comming on and off. This problems starts in the fall and carries through the whole winter here in Ottawa. The transmission will not downshift as you pull up to a stop. It feels like it is in third and stays there . It will downshift manually but then it will upshift irregularly until it warms up. Then it is fine. I was led to believe it was a manual transmission throw out bearing sticking if that makes sense because if you give it gas it will clunk into first. ???? I tend to let it warm up adequately and drive softly at first in the winter and wait for spring and it goes away. I think someone mentioned earlier that it might be some sensor that is cold and not sending proper signals. this does make some sense as the Od light is going on and off.I hope this helps. Hey I know your pain. I am just happy how well it runs otherwise and how reliable it has been. ---My problem is wind noise comming from blower area that if you turn the fan on goes awayor if you slow down.It is wind noise for sure. I think is some sort of door in the air intake sytem not closing . Any one have an Idea? sorry about the length of my letter. Thanks LF

The problem I had was pretty much warm & cold weather, not just cold. The OD light would come on and stay on and the trans would not downshift when slowed. After shutting down and re-starting the engine, it would clear the light and work OK. I was lucky, I found a cheap fix. For $19.00 at a salvage yard, I picked up a TCM (Transmission Control Module) and bolted it on myself. I have been problem-free since mid November, so I assume that the TCM was the fix.




I have a 1995 Gc Limited Orvis. Love it . But it has the same problem with the od light comming on and off. This problems starts in the fall and carries through the whole winter here in Ottawa. The transmission will not downshift as you pull up to a stop. It feels like it is in third and stays there . It will downshift manually but then it will upshift irregularly until it warms up. Then it is fine. I was led to believe it was a manual transmission throw out bearing sticking if that makes sense because if you give it gas it will clunk into first. ???? I tend to let it warm up adequately and drive softly at first in the winter and wait for spring and it goes away. I think someone mentioned earlier that it might be some sensor that is cold and not sending proper signals. this does make some sense as the Od light is going on and off.I hope this helps. Hey I know your pain. I am just happy how well it runs otherwise and how reliable it has been. ---My problem is wind noise comming from blower area that if you turn the fan on goes awayor if you slow down.It is wind noise for sure. I think is some sort of door in the air intake sytem not closing . Any one have an Idea? sorry about the length of my letter. Thanks LF

Does anyone know which points on the relay in the tcm you use to bypass it with a jumper. This is the last hing I can think to do before a teardown.

I am still having no problems at all... well, my windshield is cracked now, but so what?! ;-)

scalde, would you please let me know which pins to jumper and are the relays available at a electonics shop. Thanks, Rob

Well, I never heard from schalde so i soldered a jumper wire from pin 1 to pin 3 of the relay on the TCM circuit board and the transmission is working great. I'm going to order a new relay from a local electonics shop but it could take awhile because they have to build up a minimum dollar amount order. I'll let you know how that goes. Good luck to all.

I am having the same problem with my 1994 GC. Actually started last year and will either start out in what feels like second gear or when driving, the OD light flashes and car shifts irratically. No rhyme or reason as to when it will do it, i.e. weather, temperature, time of year etc. Car only has 84,000 miles on it. Been to three garages and Cottman and no one knows the problem.

I did the the Fault code test by turning the ignition on off-on off and then on and counting the blinking OD light.
Looks like Code 26 (blinks 2 times - pauses - then 6 times.)

Code 26 is "governor pressure sensor offset drift".

Would changing the TCM fix my problem and what would a reputable garage charge to do this?

Today a new problem and it squeeled VERY loud when putting it in reverse for a short trip to the post office and then a few seconds again when putting it in drive.

Help!!!

Your problem sounds different so I would not go out on a limb to say that the TCM will fix it. I never could get a fault code. You could try to put a jumper wire from pin 1 to 3 at the relay on the TCM circuit board and see if it makes a difference. As far as your squeal, is it your serpentine belt and is the A/C on when it does it? My daughters '95 GC does it when the a/c is on and especially in reverse. Well, good luck.