Expert: Adam Kinion - 9/2/2009

Question
QUESTION: i have a 1999 gmc sierra 1500 extended cab pickup.  when i start the engine, the 2wd button lights up and stays on.  when i push the 4wd high or 4wd low button, the light on the button i pressed begins blinking and it blinks indefinetly until i press the 2wd button.  when i press one of the 4wd buttons, i hear a "whirrr" type sound like something is moving underneath the truck.  what is my solution?  thanks in advance for your help.

ANSWER: Mike these Gm trucks of these years had alot of trouble with the 4x4 , I would say that it is the transfercase motor is whats wrong with your truck, its trying to shift ,but something is binding , or the motor is just to weak to engage the 4x4 check this problem first, thanks ADAM

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QUESTION: Adam, thanks for your quick response.  is there a specifice diagnosis method or plan i can use to check the motor or the transfer case?

Answer
Mike, you can take the motor off the transfercase and than try switching it to see if it works, if it doesnt work when it is off the truck , than its going to be ovious that it is shot thanks ADAM P.S. you can try tapping on it with a hammer while someone tries to switch it too , sometimes that works as well