I recently installed a set of OME CS009R medium duty rear leaf springs on my 86 4Runner after having stock ones that were completely shot (we're talking sitting several inches below stock height). After installing the springs I now have a vibration in my driveline that only occurs in the high end off 1st gear and the low end of 2nd, most notably around 20MPH in 2nd gear. The rear of truck now sits probably 4-5" higher than previous and I would reckon around 2" taller than stock height, as that is what the springs are rated for. I have made no adjustments to the front suspension, it is riding at stock height.

I have measured my pinion angle and it appears that it is at 2 degrees, would this be enough to cause such a vibration?

U-joints appear to be fine and I have never taken the slip yoke apart from the driveshaft to cause it to go out of phase.

I am beginning to think that it might be the rear differential causing this vibration. What do you guys think?

Thanks in advance.

 

Is that pinion angle the relative angle between the transfer case output flange and the differential flange? It should be zero between the two. If it is necessary to be off, you'll want the differential pinion to be low (by a degree or less). This is because under acceleration the pinion will try to "climb" the ring gear and will cause the pinion to come up slightly.

Did the differential vibrate before the lift? If not, it is not likely your problem. The lift wouldn't affect that. It would have to be coincidence.

When I installed the CS009R springs I had to shim the rear axle to get the pinion angle right.

The springs will settle to around a 2 inch lift. It takes a bit of time. Weight, driving, and flexing the suspension out helps.

Here's a video I made explaining how to measure the pinion angles.

www.youtube.com/watch?v=wkfndHDiH1M

 

Your video is actually the one I watched to figure out how to measure the pinion angle before ever posting this. Great videos btw very easy to follow.To answer your question though, yes, that is the pinion angle from the two flanges. I measured it the same way you show in your videos. I just ordered some 2 degree shims and I'll see what they do. Hopefully it will fix the issue.