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Q: There is a knock under the body.

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i have a 1981 gmc pickup truck it was a daily driver but then the forward gears lost and it sat for a couple years but still runs and it has a clunk when you put it from drive to first underneath but the tranny oil isnt burnt i was wondering what it was

My car has 45000 miles.
My car has an automatic transmission.

Hi there. Try putting the transmission in drive and reverse back and forth. If the clunk is heard in both directions and the clunk changes in sound pitch, then there is a universal joint that has the bearings burned up on the driveshaft. I recommend replacing the universal joints on both ends of the driveshaft to make sure that they are both functional. If you need further assistance with your clunking sound under the vehicle, then seek out a professional, such as one from Your Mechanic, to help you.

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