Tranny or rear-end problem??

GMC C1500
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GMCERIC
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I've got a 2000 GMC Sierra 1500 5.3L automatic, 1/2 ton with 236,000 km. Bought the truck used at 166,000 km not knowing if the tranny has ever been serviced or not. I haven't serviced it not wanting to disturb anything. Now, when shifting into 2nd there is a very loud clunk and the truck "jumps","pops", "kicks", followed by another smaller "kick" when shifting again. Any diagnosis here as to the specific problem would be very appreciated.
May 21, 2007 at 12:17 AM
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DANIMALGMC
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I had a similar problem with my 97 Sierra.
Pull the battery connection for about 20 minutes. This will reset the computer and the transmission computer. If the vehicle shifts normally after this, then the problem lies in the tranny.
Most likely the valve body is dirty and/or the torque converter is starting to slip.
When a problem is detected by the computer, the transmission told itself to shift hard to (believe it or not) protect itself.
If you bring the truck into a dealer for a service, have them read the error codes and this will help track down the problem.

Good Luck
Jun 12, 2007 at 2:59 PM