I just finished an 80E swap behind my 408. I'm experiencing a shudder when the TCC is locked up and it is put under a load ie. going up a hill. The truck has plenty of power to pull the hill without downshifting or unlocking but, it usually unlocks and doesn't seem to want to lock back up when it should. I need your help in diagnosing this problem. My combo is a 408/4L80E in a RCSB silverado 1500 with a Circle D 258MM Pro II 3500 stall. It feels as if the TCC is warped or isn't holding. When I check my fluid I don't see any material in it tho.

 

It sounds like the lockup clutch is slipping. Do you know the history of the converter? Did you adjust the pressure table for the TCC? Can you log data? It would be nice to log engine RPM vs input shaft speed to see if it is indeed slipping. Im sure it could just be leaking pressure somewhere inside (Im not the best tranny guy, I have lots of learning to do)

 

Do you have a vibration? If you do you may have bad verter. My cousin(brandon6.0) hisacted all werid and tranny went into limp mode. He sent it back to fti and found out a clutch went in the converter and got it fixed under warranty

 

Yes it's a vibration. A really bad one. I bought the converter new from Circle D, but I am not sure if any adjustments were made to the TCC apply pressure. I know the shift points and such were adjusted in the trans tables but I don't know about the rest. It really feels like a bad converter clutch. Maybe I can contact Circle D and they can help me.

 

That would be your best bet. That vibration mess up my cousins tranny if i was you i would give chris call

 

Ive had a couple stock ones do that.. new converter fixed it.

Has the combo been running for awhile or is this a new combo? Did it start all of a sudden or has it done it since the first drive?

 

Yes, please give me a call. Ww need to get a scanner on it to see what slip the converter is seeing. Maybe some tune adjustments can be made to eliminate it. Could be a bad solenoid or the TCC itself having issues.

Chris

 

SO I logged the truck last night and, when I command the TCC lockup it doesn't slip but, when I let the tune take over it shows 200-800 rpm slip... so can someone look at my tune and see what it could possibly be? Any other suggestions?

 

is your PWM minimun set pretty high?

 

Nonnie, the combo is new and has been slowly getting worse. I am guessing it's in the tuning after last night. I can command the lockup and it works fine, but when I let the tune control it, it doesn't want to lockup.