Torque Converter

And why do you think the TC is on it's last leg? Symptoms?

Doc

about 35-40 mph, tranny in drive, light motor load....keeps wanting to shift in and out of overdrive.

Sounds more like a TCC solenoid issue than anything else. Maybe the dreaded TCC regulator bore problem as well, seeing as how you have a 4L60e. Get the codes read and see if P1870 pops up.

Doc

if it is indeed 'shifting in and out of overdrive', that has NOTHING to do with the TC

if it is, however, shifiting in and out of LOCK-UP, the problem is in the valve body, and IF you have NOT run it too long like that (this one has the 'woven carbon' lining and is pretty bullet-proof) the problem can be correct from the valve body end.

in and out of OD = 30% RPM change (2100-2800-2100-2800 etc) in and out of LU = 200-300 RPM change max

take it to a shop that does a lot of trucks, and tell then you suspect that the 'torque converter regulator valve bore' is worn...if so, they can install a sleeve and valve to fix it

DO NOT continue to drive it like that, because the ECM will see the TC slip and jack up pressure to try to stop the slip, and the high-pressure 'BANG' shift from first to second WILL break things

TranSx-

Man, that really sounds like my problem but I have continued to drive it. For instance...i take the turn to head to my house....short street and cul-de-sac so i'm not on the gas long or hard. When I let off the gas......CLUNK but with distinct metal to metal overtones. I just thought it was the tranny shifting "hard" due to the hypertech program installed.

I'll heed your warning and get it checked out. Is it something they can put up on the rack quickly and diagnose without tearing out the entire drivetrain?

thanks.

Sounded like a clogged fuel filter too me.

GMC Gremlin

don't have to put it on the rack

just scan it for code P-1870