by Cutlass


For more information on what a TCC Solenoid does, Right click to open in a new tab

Credit: Vincent Ciulla, Auto Repair Technician, about.com

This is for the THM 125C/3T40 automatic transaxle.

Why Change Your TCC Solenoid?

Your car always stalls when you slow down to come off a freeway and the speed gets below, say 25 or 30 mph. You've eliminated an engine problem as the cause and you've read through the features on how to Diagnose Automatic Transmission Problems and Diagnosing GM Converter Lock-Up Problems. You know you have a bad TCC solenoid and you think you're in for a big bill at the dealer or transmission shop to have it replaced. Well, if you are a moderate to advanced DIY, this is something you can do yourself. It does involve opening the transmission and working with the valve body, but it can be done successfully with some care and patience. Note that these instructions are for the GM 3T40 automatic transaxle. If you have the 4T40 automatic transaxle the procedure is more complicated and should be left to a professional.

To do this job, you will need the GM J 28467-A Engine Support Fixture which you can rent at your local tool rental store. If you cannot find one, you can make do with a fence post attached to the strut towers and a chain attached to the engine support. Don't even consider using a 2x4. If you do have to use wood, I'd be scared of using anything less than a 4x4. If you do it this way make very sure it will not move or shift while you are working. Jacking up and supporting the engine from underneath is a good way around the fixture. But if the fixture is available, I strongly recommend you use it

What you will need:

1. Combination Wrenches
2. A Socket Set
3. Torque Wrench
4. Screwdrivers
5. Tube of Silicone Sealer (GM P/N 12345282)
6. Red or Blue Loc-Tite?
7. Drain Pan
8. Jack
9. Jack stands
10. A New TCC
11. Transmission Fluid
12. J 28467-A Engine Support Fixture

Before You Start:

Follow these instructions carefully. Read and be sure you understand them before you begin. Gather together all of your tools and supplies before you begin. Allow plenty of time to do the job so you don't have to hurry. Remember that these are general instructions. For more detailed instructions pertaining to your specific vehicle, consult an appropriate repair manual.

Safety is important whenever you're working around machinery. Beware of hot objects, sharp instruments and hazardous materials. Don't substitute tools unless you're sure you won't compromise either your safety or the performance of your vehicle. Never work on a vehicle that is only supported by a jack. Use jack stands to support the vehicle while you work. Work on a solid, level surface. Never jack a car up on dirt or grass.


Turbo Hydra-Matic 3T40 Automatic Transaxle

First Things First

Before starting the disassembly procedures, I would suggest cleaning the engine and transmission with an engine degreaser. A clean transmission is easier to work on and helps prevent dirt or contamination from entering the transmission during disassembly and assembly.

I'm going to break this down into three segments to make the instructions a little clearer. Okay, with that said let's get dirty!

Disassembly: Transaxle Support Assembly (Bracket)

1. Remove the negative battery cable.
2. Remove the air intake duct.
3. Remove the Throttle Valve (TV) cable.
4. Remove the power brake booster line and hose.
5. Install engine support fixture J 28467-A. Raise the engine just enough to take the pressure off the engine mounts.
6. Raise and support the vehicle with the jack and jack stands.
7. Remove the engine mount strut.
8. Remove the left front wheel and tire assembly.
9. Remove the left splash shield.
10. Remove the cross member.
11. Remove the left front ABS wheel speed sensor connector and harness from the suspension support.
12. Remove the left front ball joint.
13. Remove the left stabilizer bushing nuts.
14. Remove the stabilizer shaft from the left lower control arm.
15. Remove the left suspension support.
16. Remove the left side drive axle from the transaxle.
17. Remove the transaxle cooler pipes and plug to prevent leakage.
18. Remove the P/S lines from the P/S gear and plug it to prevent leakage.
19. Remove the transaxle mount to body bolts.
20. Remove the pipe expansion bolt from the transaxle support assembly.
21. Remove the lower engine/transaxle assembly just enough to be able to remove the transaxle support assembly and mount assembly.
22. Remove the transaxle mount from the transaxle support assembly.
23. Remove the transaxle support assembly fasteners.
24. Remove the transaxle support assembly.


Transaxle Support Assembly


J 28467-A Engine Support Fixture

Disassembly: Valve Body Cover

1. Remove the valve body cover and gasket.
2. Determine if the washer is inverted on the bolts, refer to the image.

IMPORTANT: Use adhesive/sealant compound GM P/N 12345282 or equivalent to reduce the potential for oil leaks on bolts, refer to the image.


Conical Bolts


Apply Threadlocker To Bolts 36

Disassembly: Torque Converter Clutch (TCC) Solenoid

Here is where you have to be really careful. Look and study the valve body assembly so you have a picture of it in your mind. Be careful of the small check balls and springs that they don't pop out and get lost. I found that sometimes sketching a "map" is very helpful when you are in unknown territory.

1. Remove the valve body cover. Refer to "Valve Body Cover" and "Transaxle Support Assembly".
2. Remove the wiring harness from the case electrical connector and leads from the pressure switch.
3. Remove the torque converter clutch bolt (334) to auxiliary valve body.
4. Remove the 3rd clutch pressure switch (335).
5. Remove the second clutch switch (338), if applicable.



Reassembly: Torque Converter Clutch (TCC) Solenoid

1. Reinstall the second clutch switch, if applicable. TIGHTEN Switch to 11 Nm (97 lbs. in.).
2. Reinstall the 3rd clutch pressure switch. TIGHTEN Switch to 11 Nm (97 lbs. in.).
3. Reinstall the torque converter clutch bolt to the auxiliary valve body. Install a new O-ring.
4. Reinstall the wire harness to the case and switches.
5. Reinstall the valve body cover with a new gasket.

Reassembly: Valve Body Cover

1. Reinstall the valve body cover and gasket. TIGHTEN Bolts to 14 Nm (124 lb. in.).
2. Reinstall the transaxle mount bracket; refer to "Transaxle Support Assembly."

Reassembly: Transaxle Support Assembly (Bracket)

1. Position the transaxle support assembly in the vehicle and tighten the fasteners.
2. Reinstall the transaxle mount to transaxle support assembly.
3. Raise the engine/transaxle assembly.
4. Reinstall the transaxle mount to body bolts.
5. Reinstall the transaxle pipe expansion bolt to the transaxle support assembly.
6. Reconnect the P/S lines to the P/S gear.
7. Reinstall the transaxle cooler lines.
8. Reinstall the drive axle to transaxle.
9. Reinstall the left suspension support.
10. Reinstall the stabilizer shaft to the left lower control arm.
11. Reinstall the left stabilizer bushing nuts.
12. Reinstall the left front ball joint.
13. Route and connect left front ABS wheel speed sensor.
14. Reinstall the cross member.
15. Reinstall the left splash shield.
16. Reinstall the left front wheel and tire assembly.
17. Reinstall the engine mount strut.
18. Lower vehicle.
19. Remove engine support fixture J 28467-360.
20. Reinstall the power brake booster line and hose.
21. Reinstall the TV cable.
22. Reinstall the air intake duct.
23. Reinstall the negative battery cable.

Inspect And Adjust

* P/S oil level.
* TV cable.
* Oil level.
* Suspension alignment.
* For oil leaks.

That's it! You're done! Let me repeat, this is a job for a moderate to advanced DIY. If you do something wrong or lose a spring or check ball you could seriously compromise transmission operation. If, after reading the procedure, you don't feel confident in your ability to do the job, take it to the dealer or a transmission shop.