I have had a vibration in the rear that is most noticeable at 71+ mph. I have replaced my springs w X/c ats springs, tires balanced, u joints good, and the driveshaft has been serviced and balanced. Have reviewed all the tech folders and would guess the pinion angle may be outside of the 2-3 degree range. One shop said yes but shims in the rear wouldn't be enough to correct so I took to another who said pinion angle fine that the small amount of lift would not affect it. I am attaching a few pics that looks to me that the pinion and driveshaft are in line w each other's whereas the driveshaft has a drop angle at the u joint coming from the transfer case. Anybody have this issue after a small lift or b mod c spring swap?

 

Transfer case pic

 

Front to back

 

My eyecrometer is not calibrated to +\- 1* so I'd only be speculating.

Best to go get a $10 inclometer and take some measurements.

Should be noted that even if it is with 2* you can still pick up vibrations.

Here this will help explain why.

 

I went with ATS springs for a total of ~5.5" of lift. I did not have any problems with pinion angle. You say the u-joints are good, but that would still be my place to start. Can you drive through the vibration, as in if you go fast enough, does the vibration go away or lessen?

 

Around 76-77 it lessens almost completely

 

When you are running regular U-joints on both ends of a shaft both angles need to be the same. You'll need to measure them to be sure. If you have a CV joint which I'm pretty sure mine does the lower joint needs to be inline with the shaft. Good luck.

 

Have the tires checked again. I spent a lot of money chasing a similar vibration. Turned out to be the work of incompetent tire shop + bad tires.

 

Figured it out, actually I am on step 3 of my Excursion rehab which is admitting I was in denial. Chased everything and then saw a thread where somebody showed lug centric vs. hub centric spacers and a link to a video of how they work. Yes, I had lug centric until today. I had dismissed this as I didn't think there was anyway it could be causing the vibration I had. Just figured it's an old vehicle and it would never ride as good as my truck. After switching to the hub centric spacers I now realize how bad it rode even at lower speeds. Feel like a goof chasing driveshaft balance, pinion angle, tire balance, etc. but it won't be the last time I take the long way to the correct solution.

 

Thanks for the update, glad you were able to sort it out.