Putttn

Put a add a leaf which moved me up about 2" in the rear and inserts in the front on my 96 XJ Country Now I notice a vibration from I think the driveline when under mild acceleration especially going up a long hill or when accelerating hard from a dead stop.
Sounds like a deep "hum" and I can feel it on the floorboards.

FreddyD'Apice

You need to get a Transfer Case lowering kit.

Putttn

Hmmm...even with that little of a raise?

SteveMongr

Vibration under acceleration is generally caused by two things. Ruling out any issues with worn drive-shaft u-joints.

Cause 1. Improper pinion angle.
Cause 2. Axle wrap.

The add-a-leaf is most likely causing axle wrap due to the rest of the spring pack being worn out. Worn u-joints will make the vibrations worse.

Putttn

So if it's axle wrap would the lowering kit help?

SteveMongr

No, not at all. Check for play in the drive shaft first. A lift will aggravate any slop and make it worse.
The see axle wrap try this on a level surface, have someone else in your jeep start it, press firmly on the brake and put it in drive. You watch the axle pinion/drive shaft from the side. Does it jump upwards when put into drive? Go from drive to reverse, you may see the pinion rotating a good amount. Also in 'drive' with brake applied, give it a little gas, does pinion continue rising. This is axle wrap and the only solution is replacement leaf packs. A very slight rise in the pinion is normal.
Add-a-leafs are notorious for causing wrap because they are often installed on worn or weak springs.

Putttn

Thanks for the help.

Putttn

Does it hurt to run the rig this way for a few months? Winter is still with us and don't want tot tackle this in the ice/snow.

SteveMongr

Problem is the vibrations add stress and strain to the entire driveline including pinion seal and bearings and out-put shafts. Occasional vibs are one thing, constant vibes will cause problems.
I figure if you feel the vibes in more than one place (steering wheel, seat, dash, floor, shifter) than it's a bad idea.
If you have the 242 transfer case, running it in '4 Full-Time' will likely help. This will split 40% of power to the front axle.
Another option, with the 231 TC, is to remove the rear shaft and run just the front drive-shaft, IF your transfer case is one that will not pour fluid from the rear output-shaft. Many have driven like this when necessary. Drive a little easier when doing so. The front ring & pinion is smaller/thinner than the rear.