I have been dealing with this stalling problem now for almost two years, and it has lessened my love for my car, but she's still my baby. 3 mechanics couldn't tell me, and a bunch of other car nuts couldn't either. I then talked to two retired GM mechanics that told me it sounds like the TCC switch/solenoid. I read some posts and they say to temporarily get over this problem unplug it. Is that all there is to a temporary quick fix?? I did some research and could find nothing about unpluging anything. I did find a very informative page where the guy actually documented his problem with his '88 monte carlo SS. I find that when driving in OD I am more likely to stall out at lower rpm's, whereas in D its less likely but still a problem. Has anbody actually replaced the TCC switch/solenoid, and if so please tell me how that went. I don't wanna just unplug it and hope for the best right now, but if I did unplug it would I be able to tell anything from doing that?? Thanks for taking the time.

 

The torque converter clutch staying locked up is a definite problem and will cause bucking at low speeds and on deceleration, and yes sometimes stalling. Without using overdrive, the TCC solenoid shouldn't engage, but yours COULD be stuck. Now, the torque converter on these cars, unlike some others, cannot lock up in first gear, it's second and above. So that could be why youre not stalling ALL the time, only occasionally, as long as the car is coasting down in second gear and doesn't get to first quick enough.


https://www.thirdgen.org/torqueswitch

This link tells you how to make a manual lockup switch through your ALDL connector. If you hook this up, then drive it and if you think the converter is staying locked in a lower gear, flip the switch. If you feel a difference, the converter was not locked but is now...this switch forces the computer to lock it.

Now what I can't tell you is where the damn switch is. It's probably on the transmission somewhere. On my old 4 cylinder Cavalier, it had this same problem and the plug was on the bellhousing. I unplugged it and it drives fine to this day.

Of course it's recommended to replace the switch, because running without lockup heats the transmission up more.

 

TCC getting stuck and stalling the car when you come to a light is a BIG GM issue. It happened to me personally on an 87 Grand Am, my brother had an 88 Grand Am, and my gf's mom had an 86 Grand Am (with the quad 4) ALL 3 cars had that. Incidentally all 3 cars were "fixed" by just unplugging the TCC switch from the tranny until a new TC could be obtained.

Now that the history lesson is done, I've been inside a 700R4 and I know a lot about the internals. The torque converter clutch (the actual device that locks up) is inside the torque converter, which is on the front side of the 700r4 between the transmission and the engine, bolted to the flexplate. The torque converter itself is a donut shaped device, the torque converter clutch is a clutch INSIDE the torque converter, which locks up both halves of the torque converter for greater fuel economy and lower RPMS at cruising speed typically greater than 45mph. The whole thing costs about $150 or so for a brand new OEM replacement (with a new TCC inside).

TCC lockup is controlled by the tranny itself with supervision by the ECM and brake switch. There is a solenoid inside the transmission and its accessible by pulling the pan. The only wires inside the transmission itself connect the TCC solenoid to the outside world. There is another connector on the rear of the tranny (tailhousing). Thats VSS or your speedometer. The TCC lockup connector is on the driver side, above the pan on the top side ledge of the tranny itself. Depending on model it'll be a 4 or 3 pin connector thats round. TCC operation is as follows... ECM reads road speed from VSS and knows RPM. If ECM determines TCC lockup would be beneficial it applies power to TCC lockup line which travels through the brake switch. Your brake pedal TCC switch is a normally closed switch that opens when you depress the brake.

IF ECM says TCC should lockup and IF the brake switch is not open (i.e. your not pressing the brake), THEN the TCC lockup solenoid will energize which opens a valve inside the valve body allowing fluid to move into the front pump through the TCC boost valve and moves the TCC clutch forwards, locking up both halves of the torque converter, increasing your fuel economy, decreasing TC wear, tranny load, and smoothing out your ride.

700R4 will lockup in both 3rd and 4th. If your gear selector is in OD that allows 4th gear, w/ TCC lockup. If your gear selector is in D, that allows up to 3rd gear w/ TCC lockup (and engine braking). If the selector is in 2 or 1, there is no lockup but you'll friggin hate the economy, and your engine will hate you too. You notice that in D it happens less, because 3rd gear TCC lockup happens a lot less than 4th gear lockup.

There are several points which may cause the TCC to NOT unlock as it should.

1. The clutch itself could be bad inside the torque converter. Replacing the torque converter would resolve this as they are not serviceable by you. Even tranny guys don't rebuild TC's. This is what happened to all 3 grand ams above.

2. the TCC solenoid could be getting stuck open, thus keeping the passage to TCC apply open. Replacing the TCC solenoid on the outside of the valve body, inside the pan would fix this.

3. The brake switch could be faulty and not opening all the time. Look above your brake pedal to find one or more plastic devices. One should have a thick vacuum hose on it, which is for your cruise control - the other has only an electrical connector, thats the TCC brake switch. Check it with a meter its a simple switch that should open when you hit the brakes.

NOTE: if you simply want to keep the TCC from lockup then just unplug this connector. Your tranny will hate you if you run on the freeway, it will get a lot hotter and reduce its life, and your fuel economy will suffer. I personally drove for 3 months like this (unknowingly - only street up to 50-55), and my tranny is still rolling It might keep you going until you can afford a rebuild.

4. You could have some serious damage to the valve body, which is allowing some pressure from some other circuit to pressurize the TCC apply passage. THis is rare, but possible.

In short its probably rebuild time, if your going to get to the TCC solenoid then you may as well inspect the VB, and if you do that, you should just get the tranny rebuilt. Its probably time anyways, and depending how long this has been going on you might have something seriously wrong.

As for what to do right now.... Just unplug the brake switch and drive in OD. If that keeps the car from stalling at lights, then you definitely know what has been happening.

Essentially your driving at 45+, your TCC locks up both halves of the TC and your cruising happily along. When you get to a light, you apply the brakes. Now here is where an understanding of how your TC operates is helpful.

Think of the torque converter as an automatic clutch. when the engine RPM is lower than the input shaft speed of the tranny, it allows it to freewheel on that side. Just as if you were driving a stick and were to depress the clutch. Except with an automatic it happens by itself based on hydraulic pressure within the tranny and torque converter.

Now the torque converter clutch is just like that except that it acts to "lock" the engine to the transmission, to reduce TC slippage that normally occurs. When you hit the brakes you want it to disengage, otherwise you stall the engine, just like if you hit the brakes on a stick, without using the clutch.

By unplugging the brake switch you prevent lockup from happening at all. If this solves your problem, then you can drive the car for a few weeks off the highway to get to work and whatnot until you can afford to get either the TCC solenoid, the brake switch, the TC itself or the transmission fixed.

If it still happens then your looking at needing a tranny rebuild to fix it.