Manual tranny banging hard at any gear or speed

2001 GMC SIERRA
198,000 MILES • 6.0L • V8 • 4WD • MANUAL
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JC75
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Hard banging from under cab at any speed. I can feel it in the shifter. Acts like trying to jump outta gear or into four wheel. Does it really fast n makes truck jerk a bit. Does it in any gear any speed. Might go two miles n not do it once then might do it 5 times in next mile. Does not do it in four wheel at all. I’ve changed tranny grease n checked transfer case n it’s full. I’ve visually inspected everything n I’m at wits end. Replaced u joints also. Could orb rear end issue but sounds like sound is coming from tranny or transfer case. Email@[email protected]. My dad’s a pretty good mechanic n I have pretty good knowledge around vehicles
Jan 27, 2019 at 5:57 PM
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ASEMASTER6371
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Good morning

The first thing I would check is the transmission mount and be sure it is not broken or worn out allowing too much movement.

Does the transmission pop out of gear while driving?

If all that is OK, then see if there is a lot of free play at the output shaft of the transfer case. If there is, then it could be a transfer case that is worn out.

Roy
Jan 28, 2019 at 3:26 AM
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JC75
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Thanks for your reply Roy No sir it does not jump out of gear. It does whine a little in fifth but I just figure that’s age. Output shaft does not have much play if any. Jacked up tranny and mount seems to be fine. It doesn’t make a sound when in four wheel. Someone told me maybe a loose chain in transfer case but all is good in four wheel. I’m bumfuzzled. No one I’ve talked to has ever had this problem.
Jan 28, 2019 at 4:54 PM
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ASEMASTER6371
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If the mount is good, then good chance it is an internal issue with the transfer case.

Roy
Jan 28, 2019 at 5:02 PM