GMC Transmission Problem?

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I have a 2002 GMC Envoy and have problems with excessive rpm's and slow shifting after the truck sits for 3-4 hours. After about 3 miles it seems to run OK, but upon startup, the engine roars and the rpm will run over 3000 before it shifts. I thought it was due to cold weather, but it has been in the upper 50's this week, so that shouldn't be it. The transmission shows a full fluid level.

Is this something I can take care of or should I head for the dealer?

posted by  Moonraker

You might want to get it looked at it, It might be a vacum modulator (if equiped) or a computer problem or before going to the extrems and spending alot of money try changing the fluid and filter. This should be done every 30,000 miles or every 24 months. This is just my :2cents:

posted by  Caddyranger9190

with the RPMs shooting up as you described, it sounds like a vaccum leak. the transmission will shift funny because the engine isnt operating normally. its like reving the truck and shifting, it might bang into gear, or stall out on ocassion. the obvious advice would be have it looked at if your not sure of the problem. sometimes a simple diagnosis will reveal something simple...sometimes not. but in the case of your truck, its hard to say what it could be. could be a few things. but you probably wont know until its checked in person by someone.
my guess is a vaccum leak in the engine.

posted by  nattereri2000

our gmc did the same thing (what has that piece of crap not done) it was and sounds like a bad timing in the computer to me.

posted by  rstifle3000

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