Rear driveline vibration

[mongocanfly]

Did you try flipping it 180deg?

[72cs20]

Originally Posted by mongocanfly

Did you try flipping it 180deg?

Not yet. I'll have more time tomorrow to experiment with it.

[duallyjams]

Good info on setting pinion angle https://4xshaft.com/blogs/general-te...veshaft-angles

[kwmech]

It's either 1 spline off or 180 degrees and 1 spline. When the shaft was built and balanced it was not welded together 2 teeth off to make it close. U-joints were in phase with each other. If it vibrates in either place you'll need to take to a shop and have it re-balanced or something is loose in the CV. Look at the slip where welded to the tube and closely at the sliding part. Most driveline shops will have a marker like a line, couple of dots, arrow etc. marking both pieces where it should be for instances like this. PLUS the pinion (in the 3rd pic) is too high. 1st pic looks correct. It needs to come down about 4 degrees or more (2'' ish). Under load, the pinion is going to climb higher than that. Pinion needs to point at the bottom of the t-case yoke so when it climbs it points directly at the center. Make sure the rear u-bolts are the correct size and torqued down to specs

[72cs20]

Originally Posted by kwmech

It's either 1 spline off or 180 degrees and 1 spline. When the shaft was built and balanced it was not welded together 2 teeth off to make it close. U-joints were in phase with each other. If it vibrates in either place you'll need to take to a shop and have it re-balanced or something is loose in the CV. Look at the slip where welded to the tube and closely at the sliding part. Most driveline shops will have a marker like a line, couple of dots, arrow etc. marking both pieces where it should be for instances like this. PLUS the pinion (in the 3rd pic) is too high. 1st pic looks correct. It needs to come down about 4 degrees or more (2'' ish). Under load, the pinion is going to climb higher than that. Pinion needs to point at the bottom of the t-case yoke so when it climbs it points directly at the center. Make sure the rear u-bolts are the correct size and torqued down to specs

There are no alignment marks on this driveshaft.

I did a lot of experimenting today and found that three splines over from the original position is the sweet spot, no vibration. Turning it 180 degrees results in vibration.

The pinion angle is good. The shaft is 10 degrees down and the pinion is 8 degrees down. This should allow for a 2 degree upward movement of the pinion, should there be any.

All the suspension components are properly sized and torqued to spec.

You are right. The bottom line is that I will be taking it back to the shop that built it so they can make it right.

I'll post back the results. Thanks everyone!