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- - tranny problem (https://67-72chevytrucks.com/vboard/showthread.php?t=301947)

faribran

08-05-2008 12:07 PM

tranny problem

i have a 2000 GMC 1/2 ton truck with auto overdrive..
the problem i am having is... at cruise speed the transmission will shift up and down... doesnt seem to be slipping... but maybe the lockup is going in and out.... anyone here have any ideas.... plz
thanks
Rich

WLPTMP

08-05-2008 08:36 PM

Re: tranny problem

sounds like a pressure control solenoid

79gmcsierragrande

08-05-2008 08:49 PM

Re: tranny problem

Sounds like auto's suck.

Sorry that was mean.

D13	08-12-2008 10:22 AM

Re: tranny problem

Hold the truck at 55mph, gently push the brake (just enough to turn on the lights but not enough to actually apply brake). That will kick off the converter, note the tach reading, let off the brake, the tach should drop 3-400 rpm. that's the TCC engaging. If it doeen't, that's bad, next you'll need a scanner to determine if it's getting the signal, if it is, then it's the solenoid in the trans or a trans/converter problem.

kevinr1970

08-12-2008 08:28 PM

Re: tranny problem

Quote:

Originally Posted by D13 (Post 2845653)

Will this still be the same on one of the newer fully electronic tranny's?

Longhorn Man

08-26-2008 09:38 PM

Re: tranny problem

all of these 99 to date are fully electronic.

D13	09-03-2008 11:31 AM

Re: tranny problem

They all work the same. Brake shuts off TCC. ECM/PCM commands it on.

Only odd one are early units, particularly diesels, where the TCC may be hard wired to 3th gear or thru governer pressure.

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