TCC troubleshooting and repair

by Oliver Scholz

The symptoms for a bad TCC are obvious: If your car comes to a stop and the engine stalls, but restarts (in neutral), and immediately stalls again if you put it in drive, your TCC is shot. You can verify this by disconnecting the plug facing forward on the transmission near the oxygen sensor. If the symptoms go away, your TCC is bad. (If the symptoms stay your TCC may still be bad). This is caused by sediment sticking to to the electromagnetic portion of the solenoid. The part number of a replacement solenoid with an improved seal is P/N 8652379.

Replacing the TCC seems difficult at first, but it can be done with the transmission still in the car. The procedure described is for the V6, but the L4 will be similar. You'll need an assortment of wrenches and sockets, 10mm, 13mm and 15mm, and a couple of short and long extensions. Do yourself a favor and get a gasket scraper.

I decided to change the tranny fluid while I was at it. The reason was that I didn't want to get "Frised" (to get frised: to get a shower of transmission fluid in the face) when removing the side cover. I don't know how much fluid there is in the side pan if the tranny is still full, I just wanted to be on the safe side. So maybe you can do it without changing fluid, I just did. I cleaned the oil pan, cleaned the old gasket from the transmission, installed a new filter and filter gasket, and put the bottom pan on again. Very simple task, but my pan was very dirty and it took half an hour and a dozen shop towels before the pan was clean again. The same goes for the bolts.

Next remove the bracket on top of the tranny that holds the transmission coolant line. Otherwise you won't be able to access the bolt underneath it. Disconnect the shifter linkage at the tranny and move the cable out of the way. Finally remove the air intake duct between the air filter and throttle body. You need to do this to be able to remove the side cover through the top later on, and it makes accessing the bolts easier.

Remove the driver side rear wheel and support the car well with jackstands. Remove the push in rivets that hold the mud flap in place. You'll see which ones to remove, and if you break them, don't worry, they're cheap. Move the mud flap out of the way and you can access some side cover bolts through it. Most bolts can be easily accessed now, some from the top, some through the wheel well, some from the bottom (it will be obvious how to access each bolt when you see it). I used a 1/4 inch ratchet for most bolts, they are not tight (but space is). You need quite a bit of extensions when removing bolts through the wheel well. There are a total of 11 bolts. The most difficult one was the one between the two transmission coolant lines. I left the two bottom bolts in before prying on the cover. There will be some transmission fluid leaking out of the bottom, so be prepared. Now remove the last two bolts and remove the cover through the top. I cleaned the cover real good with brake cleaner and also cleaned the 11 bolts. They turned out looking like new again, but it took a while.

Now comes the main part. I used a GM replacement TCC kit. Check with your dealership for the latest part number, GM keeps changing the design all the time. The TCC is bolted to the transmission with a Torx bolt (at least on my 85, other years may have a different bolt). Removing the bolt, the TCC and the wires from the 3rd gear switch is a snap. Removing the connector from the connector inside the transmission was a little difficult because you can't see it. There is a tab on top which you need to lift up. Use a mirror and the new part for reference.

The new TCC comes with a bracket that must be attached to the valve body. It also includes a drawing that tells you where to mount it. Easy. Putting the new TCC in (put some tranny fluid on the rubber ring), and connecting it to the third gear switch was also a snap. The wiring snaps into the new bracket you just installed. Now comes the hardest part. You need to put the connector into the connector that leaves the transmission. If you think removing the old connector was difficult, you're up for a challenge. Simply put, the TV-cable is in the way. I tried to remove it, without success. So I fiddled the connector in there with one hand through the wheel well, "feeling" where it should go, because there is no way you can see it. If the TV cable wasn't there it would probably have been easier. But it can be done with the TV cable in there as well. It took a while though. Once that's done, the hard part is over.

Clean the remains of the old gasket from the transmission (this also took me some time since some parts were hard to access, and the cork gasked was virtually baked to the transmission). This is where the gasket scraper comes in handy (I didn't have one though, and the shops were already closed). Clean the mating surfaces with brake cleaner, wipe dry (make sure there's no fluid on the surface!). Now reinstall the cover and new gasket, and tighten the 11 bolts (but don't overtighten!) I found it impossible to use a torque wrench on any of the bolts, due to space constraints. So I torqued them down by "feel". Reinstall the coolant line bracket. Now is the time to adjust the shifter. Put it in neutral, move the gear select lever on the tranny in neutral as well and reinstall the cable and nut. Put the mud flaps, rivets and the wheel back on, put the proper amount of tranny fluid in and you're done.

It took me a few hours for the whole procedure, but I'm sure it can be done in less time, some suggested an hour, if you know what you have to do. Hopefully this procedure helps you save some time, I'm sure I could do it in two hours, maybe less, if I have the right tools. (Don't flame me writing you can do it in 30 minutes, I did this for the first time, so I exercised care in everything I did, and I took my time). After all, this is supposed to be fun and not stress (so bring along a six pack and some good music, and it'll be a fun project).

I didn't have a gasket scraper for instance and it took me 90 minutes to properly clean off the old gasket with a sharp knife and a screwdriver. I also thoroughly cleaned everything and chatted with the neighbors, which didn't help. But plan for the unforseen and give yourself plenty of time to work on this job, and it won't be that difficult.

Lawrence T. Mazza also did this on his 88, and he has a few notes. First, he didn't disconnect the shifter cable, but he was able to access the bolts from the top. Maybe the 88 is different. The big thing is that he didn't remove the fluid from the tranny! When jacking up the driver side as high as it goes, only a few drops come from the tranny when the side pan is removed.

Another note comes from Ogre: Replacement of the TCC solenoid is a pain on 86.5 and newer with 4 cyl and automatic. GM went to a single tranny mount on these. There is now a huge bracket covering the side of the transmission. Very annoying. You have to remove the bracket and support the transmission before you can get the cover off. While people are in there..... they should also replace the third gear switch. It's next to the solenoid.

Here's Chuck Kichline's description of how to replace the TCC.

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