I'm tracking down a vibration problem and have measured my driveline angles after recently putting on a 2" lift using Crown HD leaf springs and Moog HD coil springs. Stock replacement shackles.

Is it normal for a leaf spring lift to move the pinion angle upwards?

I took my measurements with a magnetic angle gauge in the following places:

Transfer case angle at the flat case surface below where the kick out for the 4wd indicator is. Photo is NOT mine, I don't have an SYE.




Pinion angle at the machined flat surface beside the rear cover. (Tom Woods image)



I have angles of 82.5 for the transfer case and 79 for the pinion. I also measured off the u-joint cap at the transfer case yoke and got 8.5 degree and measured from the rear u-joint cap and got 11 degree.

I believe this means I need to point the nose rear diff down at least 3 degrees, possibly 4 to allow for 1 degree of tilt up during acceleration.

How could things be so out of whack without a huge lift? Could I have measured wrong?

Replace your ujoints.

I did the exact same lift recently on my girls 98, had the vibes, replaced u joint and still vibes, dropped transfer case and no more vibes. Just my experience...

Already replaced the rear u-joints with Spicer 5-1310X. Front driveshaft is temporarily removed to eliminate front vibes.

Thanks Guntar, how much did you end up dropping the tcase? What speed were the vibrations?

I got a 1 inch drop off amazon, aluminum spacers and new bolts. Most around are a standard 1 inch drop. Hit them with some black paint so they didn't stand out so bad. She loves it cause it doesn't shake!
They started about 25-30 and got so bad you couldn't feel them around 50

OP, you have vibrations from the front and rear shafts?
how many miles on your xj? and u joints?
you probably should not need a drop kit for only a 2 inch lift.
I agree with replacing u joints.

No, the vibrations remained after pulling the front dshaft. It's from the rear.

XJ has 200k miles. Brand new spicer 5-1310x u-joints in the rear.

I re-did the measurements with a nice digital angle finder and got a 2.5* difference between the transfer case and pinion angle. The pinion definitely needs to come down 3-3.5*. Going to try some leaf spring shims out.

Where do you get leaf shims? I may be in the same boat.

I just measured my T-case and rear axle pinion angles similar to the OP and got about 3.0-3.5* in the rear and 4.0* in the front. Seems pretty damn close, and the driveshaft itself was at about 11-12*. Can I safely eliminate the driveline angle as the cause of my vibrations under throttle and start thinking about replacing the original (I'm assuming) u-joints?

Did you figure out how to fix your vibration? I believe I am having a similar issue after install the same setup.

I machined 3 degree leaf spring shims and installed them but this caused the driveshaft to pull too far out of the slip yoke causing the splines to bind up under heavy torque loading. So I removed the shims.

So the next best thing was to drop the TC. I think I ended up dropping it 5/8" and the vibes are mostly gone. I'm not totally happy dropping the TC but it was the easiest option for now.