Unloaded vibration

[Billw69]

Anyone experience a driveline vibration while in an unloaded condition? Curious about what might cause a vib above 70 mph, and is amplified when pushing in the clutch, for example during a shift. This vibration increases in frequency above 70mph.
The car has a new clutch, rebuilt transmission and axle, replaced driveshaft and yoke as well as u joints.
Thanks

 

[basstrix]

I've had a failing pinion bearing or loose pinion nut cause noise and vibration unloaded but quiet down when loaded.

 

[Billw69]

Thanks, no options are off the table yet. Input bushing to bent axle…… although I’d think a bent axle wouldn’t change frequency when I push in the clutch. I find myself wondering if it could be related to the driveshaft or the hardware on either end. I’m going to clock the driveshaft 180 degrees in the axle yoke and double check the u bolt torques as my next move, (least invasive).

 

[basstrix]

Another case I thought of was one of the alignment tabs on the pinion yoke was worn down...probably from running with a loose u-bolt. The cap of the u-joint was able to move outward and let the u-joint move back and forth along the trunnion axis. I know the vibration changed with and without load, but I can't recall how it changed. I welded up the tab and re-ground it and the vibration went away.

 

[Billw69]

Good input, thanks. I did notice that the tabs in the pinion yoke made for a VERY snug fit, as in I have to use a pry bar of appropriate nature to unseat them.