HELP!!!!! 94 GT won't won't shift out of overdrive

My 94 GT just started this the other day:

It is an auto trans, and runs just fine until it hits overdrive. From there it takes almost flooring it to get it to downshift and then is skips down a couple of gears (into the passing gear). If I use my left foot and depress the brake pedal enough to activate the lights without applying the brakes, it will shift out of overdrive and only drop down one gear like it should. But as soon as I take my foot off of the brake pedal, it shifts right back up into overdrive. This only happens at highway speeds from about 40-45 mph up and doesn't seem to happen until the car warms up.

Any ideas? Please help, as this is really really bothering me.

I just had the tranny fluid flushed and filled yesterday, and it made no difference. I have no loss of power, just the unwillingness of the car to come out of overdrive once it gets there.

It sounds like you could have a bad TCC solenoid. By the way, a fluid flush on high mileage tranny = bad. There's lots of crap that has been worked into the tranny into all the nooks and stuff, and when it gets flushed, it breaks it all loose - and could actually cause slippage.

yeah, TCC or the vacuum solenoid hose or valve. If you literally had it flushed, sigh, that could really be a problem.

I might suggest, outside of the two controls to check out, get the fluid drained again, NO flush, that may help if that is the cause [all the junk, etc. broken loose by the flush], to get the junk out of the trans.

Wish ya well, let us know how things go.

http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/0e/5b/f5/0900823d800e5bf5.jsp

In case it may be the modulator, at least it a fairly easy check. Especially check the hose.

Just to clarify, when I had the tranny flushed, it was done as you all are saying, flushed, filled, drained, filled. The flush sucked out a tremendous amount of crap, and there wasn't much left in the pan after the refill/drain, before it was filled and finished.

It was doing the same thing before the service, except it wouldn't downshift if I activated the brake switch. Now, after the service, it will at least downshift if I hit the brake switch.

How can I tell what tranny I have? Is it possible to unplug the TCC for a test without losing the 1-2 3-4 shifts (I know it depends on the trans)?

There are several auto trans.

125C

3T40

4T60E

To find the right one, there is an I.D. # stamped on the housing. Differing trans. have different I.D. locations, it may be useful to list your engine size, which is the 8th letter of your VIN #.

Generally, the 125 is mated to the smaller 4-cylinders, and the two others mate to the 3.1. Others may have better info. for you.

Its a 1994 GT with a 3.1, the 8th digit of the vin is an M. From what I can tell its the 4T60E.

Can I unplug the TCC without any ill effects to see if that is the problem?

If so, where is it located (please be specific)?

Thanks!!

I think I have it temporarily fixed, not sure for certain. I got the Haynes manual out and looked at the wiring diagram for the 3.1 engine controls.

I found the tranny plug (wasn't exactly hard to see, sitting right on top on the front, under the throttle body) and located which wire was the feeder for the TCC solenoid. Since I didn't want to cut anything and there wasn't a separate wire going to the TCC externally, and I didn't want to lose my shift points from 1-4, I pulled the whole tranny plug, removed the retainer from the plug and pushed the pin that is associated with the TCC feeder wire out of the plug assembly. I tied it back (insulated it as well) and put the plug back together and reisnerted the plug.

Went for a test run around town (only have 4 blocks in town) going slow to see what would happen. Sure enough, everything seems to be working fine. The tranny still shifts into overdrive, but just doesn't go into full lockout mode, syncing the plates in the converter.

The only real drawback I can see on a temporary basis is the loss of a few miles per gallon due to slightly (about 250) higher RPMs. As far as I can figure based on research I've done all over the net, this will be a workable fix until I can save the $$$ to get a new TCC installed. Money is really really tight right now and it may take a couple weeks to save the quoted $375 to get it fixed (mostly labor).

If you think this quote is high, please let me know so I can check around. I just went to my usual mechanic, since he has always been really fair to me on other stuff. ($450 total for a new intake manifold gasket and injector harness, a bunch of other parts included too, like o-rings, PCV valve, serpentine belt, etc...basically tuned to whole thing up when he was replacing the gasket) I thought that $450 was really reasonable considering.

Anyway, If there are any immediate drawbacks from having this wire disconnected for about 2 weeks, please let me know so I can take care of it before I inadvertently destroy the tranny ( I don't drive hard at all, too much construction and traffic during my work commute to drive hard)

Thanks in advance for any advice you can offer, and the sooner the better!!

JTK, I ran a search of your prob. within AF, general consensus seems to concur that disconnect of the solenoid is for a temporary fix only to get home or to a shop. It seems that to disconnect the solenoid will put strain on the trans.

Run a search off the search bar in AF, using AF, text in TCC and see what they say, it generally is a temp. fix. just to get home or to shop.

Thanks!!

I seemed to find the same thing when I looked on AF and other locales.

I don't really have a choice but to have it disconnected for a week or so. I guess I'll just have to keep my fingers crossed and hope my tranny is good enough to hold up (I hope its not a tremendous strain) for a week.

Well, I think $375 just to replace the TCC seems a bit much, but then I've never had to try to replace one back-yard style, so I really can't say.


I think if you stay at lower speeds, perhaps even stay in third [if you running at lower speeds], that shouldn't hurt the trans.

ok...I disconnected the TCC as per a conversation with my mechanic (over the phone). Here is how:

According to the Haynes diagrams for the 3.1 there are 2 wires in the multi wire plug that plugs into my trans (a brown one and a pink one)

I pulled the contact for the brown one and left the pink one connected. When I took it for a drive it seemed to work fine for a day or so. Yesterday it really started acting up.

I'll be going along the highway just fine, and all of a sudden it will act like its starving for power. If I give it more throttle it bogs down even further, bucking and carrying on the whole time, eventually stalling out.

Sometimes it will fire right back up and run fine the rest of my commute. Other times it will take like 10 tries to get it running (it just fires and sputters out right away when its acting like this). Once it is running again, it will run ok for the balance of my commute (30 miles each way to work and back)

The problem seems to arise after the engine has had plenty of time to reach operating temp and have the engine cooling fan kick on a couple times (like it traffic).

Today, for example, it died on the turnpike. It just stalled out and acted like I just described...wouldn't start and keep running. It would start and then sputter out. It took a good 5-8 tries to get it running, and then another 3-4 tries to keep it running once I put it in gear and tried to accelerate back on to the road. It would stay running when I put it in gear, but as soon as I hit the gas to pull out, it would die. No sputtering or anything, just stall right out dead.

Here are a few things that I think it could possibly be:

Failing coil pack
Bad ign. module
blocked up Cat. Conv.
fuel filter (going to change that this evening after work)
spark plug / plug wires (how can I check the wires, don't get continuity with a Fluke meter on any of them)

Also, could it be the trans? If so, what could be the problem.

I read some threads here about the Crank sensor. Could that be it too? If so, where is it located and how do I change it?

I know a little (except when it gets into real troubleshooting, as I can do plugs, wires, brakes, oil, etc...the basics) about cars. I was able to figure out the wiring for the trans plug because I can decifer wiring diagrams if I look at them long enough. (At least I hope I unhooked the right wire)

Do you think any of these possibilities could be the culprit? If not, any other suggestions?

If so, how do I check these things? Can I check the coil packs? If I can what should I do and what should I be looking for? Same with the ignition module and plug wires?

Any help here would be enormously appreciated. I really would like to avoid taking my car to the shop (don't have the $$ to pay someone else to fix it) unless it is absolutely necessary.

I have a 94 GT, 3.1 and I am not sure what trans I have. I think the 4t60e, but I am probably wrong about that. I'm just getting really depressed about this issue because I REALLY need my car to be running reliably for work and I can't afford/don't have the credit to get anything else.

Again, any and all help is appreciated.

Thanks everyone.

K,
1] The TCC should not be your prob. with the engine dying like U describe. The TCC deals directly with the trans., not the engine.

2] While I may get into trouble with the moderators on this, everything you are describing is so lengthy, I would spend mucho time giving links.

Therefore, and I do apologize to the Mod.'s who monitor the forum, I'll take the blame, register for this site and surf it. www.autozone.com (http://www.autozone.com).

I am doing this just to help a guy out, not to promote any one thing over any other. I hope this will help the dude narrow down his prob. so we can better go with advice for the prob. his ride has.