99 Bravada, 165K, tranny "serviced" by PO at 125K, no idea what was done. Fluid looks pink, no stink.

During my commute this morn, at 57 mph and after half an hour on highway, torque converter suddenly stopped locking. Came to a red lite, stopped, found I now have a hard, jerky upshift from 1 to 2 which happened 3 more times before shutting off at work. All other shifts feel normal, trans doesn't feel like it's slipping. Could this be due to low ATF?? The crummy GM dipstick tube design makes it tough to tell just what the fluid level is when hot. I'll check it again tonight when it's cold. Thanks!

 

Does it have any transmission codes pending or set? You can also look at 1-2 TAP cells for abnormalities in pressure adjustments. Probably the TCC is disabled because PCM is recognizing another problem.

A cheap scanner that will read trans codes including display of TAP cells, TCC operation, etc.

https://blazerforum.com/forum/2nd-ge...-retard-90496/

My condolences, just paid $2300+ to get my tranny overhauled by Precision.

 

I will have to get my son's code reader out, or stop by AZ for a code-read. After being parked for 9 hours at work during the day, it ran fine on the way home and has been fine since then. However, and I don't remember whether it did this before, I've noticed recently that when starting out cold in the morning, the TCC doesn't lock up in OD for a few minutes. I'm hoping this is because the engine isn't fully warmed up: it seems to lock when the temp gauge needle gets to the line between cold and 210 or whatever. Right now, and for the past month or more, I've had codes such as P0440 pertaining to the evaporative emissions system; I suspect there's a broken vacuum line on top of the fuel tank or maybe the solenoid on the tank is broken. It weeps some gas whether empty or full. Waiting for warmer weather before dropping the tank to fix. And from time to time, P0310, indicating an open transfer case motor, shows up but not very often. That may just be a dirty plug/connector; the AWD seems to work even with that code showing.

 

I had the same thing going on, i went to amazon and bought a new valve body and installed it.Problem solved. Not a bad job, just take your time

 

Engine does have to get warmed up before PCM will enable TCC.

 

Sounds like the trans has an issue, when the code is thrown the trans goes into failsafe mode and jacks up the pressure causing the harsh shifts. When you turn off the vehicle the computer resets and it acts normally until the code is thrown again.

We need to know what code(s) is present before we can diagnose anything.

 

Did you get it fixed??? was it a P1870 or P740 Code that was setting??? TCC slip code or TCC short or open.

 

Sounds like the clutch inside of the torque converter is gone out. If you are a few quarts low on fluid it will cause issues. I know it's a pain, I just paid $1050 to have Geared Up build me a new one on my mud truck.