TCC Question

[t-topflyer]

Turbo Buick shifts good and firm into all gears. In 4th gear, the TCC engages rarely if ever. It might engage when it first warms up, but quickly shifts back out and only engages occasionally and shifts quickly back out throughout the rest of the drive. Any thoughts on what I should do to correct this problem?

 

[Grimster]

Ok in my ignorance I've gotta ask, how can you tell that it's not locking up? What do you look for or feel that alerts you to the fact it isn't locking?

 

[t-topflyer]

To save gas mileage in high gear, the TCC engages via signal from the TCC solenoid once a certain speed is reached. In high gear during normal operation, it will seem like it shifts smoothly again followed by a drop in RPMs. This is not another shift, but is the TCC engaging. You can mimic this disengage/engage behavior by tapping the brake pedal around 55-60 mph then letting off. When it's functioning properly, you will see a jump in rpms as it will disengage by tapping the brake. You may also feel it. Once you let off the brake pedal, the RPMs will drop again as the TCC engages again. This normal behavior is absent in this case except as stated above. So, I'm thinking it might be the solenoid which is a very common problem in these transmissions, but I would like a second opinion before I start down that road.