I recently installed a set of Dorman 4.10 gears in my 08 Silverado. Backlash was about .007 to .008. Anytime I get around 80-85 MPH the drivetrain starts to vibrate at a really high frequency (like a massage chair). Needing help with the trouble shoot asap.

 

Assuming your gear install is perfect, I suspect that your problem is with the driveshaft. It now is spinning faster than before with the lower gears. You may need a better driveshaft, balanced and capable of spinning to the new higher rpm without reaching critical speed. What gears did you have before the 4.10's?

 

Had the factory 2.73's....very "gutless". has a 5" aluminum drive shaft.

 

.007-.008 on a new gear set it on the loose side IMO.

But that's not the cause of the vibration. Try indexing the drive shaft 180 degrees out. And see if that helps any.

How was the yoke removed? Hopefully not a big hammer?

 

Didn't touch the yoke with a hammer. Used a decent size punch to pop the old pinion out. Yoke popped right out after that. The driveshaft & yoke had corrisponding white lines marked on'm. I lined them up the same when reinstalling. 5" Alum driveshaft. Do you think if I didn't pre-load the pinion bearings enough it could cause a vibration at higher speeds?

 

& what would you recommend for a good backlash for a new gearset?

 

Ive never seen a newer truck with 2:73 gears care to share the rpo code in the glove box?


As for the vibration with that tall of a gear going to that short of a gear i bet the driveshaft isnt balanced to handle the spinning its doing now. Id take the driveshaft to be balanced for those new gears

 

Gu2 2:73
gu4 3:08
gu5 3:23
gu6 3:42
gt4 3:73
gt5 4:10

 

i'll have to have a look later. Where in the glove box is the rpo code? Thanks for the info everyone.

 

If the bearings have absolutely zero preload and the pinion is actually moving, ya it would have a vibration. But it would probably have a horrible noise also.

If it was marked before it was removed, I would still try switching it 180 out to see if it helps. If not check the balance on the shaft.