T56 Clunk in gear when accelerating
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Teching In
Joined: Sep 2016
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T56 Clunk in gear when accelerating I have a 1997 Trans Am LT1 T56 I just purchased a month ago. The guy had the engine rebuilt, had a small cam put in it, kooks headers, underdrive pulley, and had it dyno tuned. It was missing a few things so I couldn’t test drive it before I bought it, but I got it cheap enough to feel comfortable with that.
Now that it’s home I went on a little spin and I’m having this loud metal clunk that sounds like the driveshaft hitting the floor board, you can feel it too. When I’m driving in gear and accelerating it clunks and the clunking sound increases in pitch and frequency with speed. When I press down on the clutch pedal to change gear the noise gets much quieter, then I shift into 2nd, release the clutch, and the noise is back and louder in 2nd than 1st gear, same goes with 3rd gear being even louder and more violent sounding than 2nd. If the vehicle is in neutral (moving or sitting still doesn’t matter) and I rev up the engine, there is no noise. No squeaks or squeals, just an obnoxious clunk that sounds like something is about to fall out of the car.
I got underneath of it while it was jacked up and in 1st gear moving and checked the driveshaft out, it isn’t making contact with anything so that rules that out. It was missing one of the u-joint straps in the rear so I replaced that but the noise stayed the same. The sound was definitely focused around the transmission but also echo’s down the driveshaft so it’s heard all over.
I’m kind of new to manual transmissions and clutches, anyone have any clue what this could be? Loose flywheel/pressure plate bolts? Bad clutch? Bad pilot bearing? Input shaft? Thanks in advance!!
Now that it’s home I went on a little spin and I’m having this loud metal clunk that sounds like the driveshaft hitting the floor board, you can feel it too. When I’m driving in gear and accelerating it clunks and the clunking sound increases in pitch and frequency with speed. When I press down on the clutch pedal to change gear the noise gets much quieter, then I shift into 2nd, release the clutch, and the noise is back and louder in 2nd than 1st gear, same goes with 3rd gear being even louder and more violent sounding than 2nd. If the vehicle is in neutral (moving or sitting still doesn’t matter) and I rev up the engine, there is no noise. No squeaks or squeals, just an obnoxious clunk that sounds like something is about to fall out of the car.
I got underneath of it while it was jacked up and in 1st gear moving and checked the driveshaft out, it isn’t making contact with anything so that rules that out. It was missing one of the u-joint straps in the rear so I replaced that but the noise stayed the same. The sound was definitely focused around the transmission but also echo’s down the driveshaft so it’s heard all over.
I’m kind of new to manual transmissions and clutches, anyone have any clue what this could be? Loose flywheel/pressure plate bolts? Bad clutch? Bad pilot bearing? Input shaft? Thanks in advance!!
Last edited by 99trans-am; Apr 3, 2020 at 09:17 PM. Reason: Drove the vehicle more thoroughly and found some new information
Could be the input shaft (which is also 4th gear) is missing or has a broken tooth, which would explain why the noise is in all gears (and gets worse as you go up). No real easy way to tell without pulling the trans though.
