I have a 96 cherokee with a 3 inch lift and 31s. I put new leaf springs on that have a 2 inch lift with one inch longer than stock shackles and 3 inch blocks in the coil springs up front. Drive shaft is vibrating. What do I need to get and do to fix this?

 

It is likely from improper drive-shaft angle. Or the u-joints are worn.
Above 3" of lift the rear drivesahft gets replaced with a double-cardan driveshaft and the output shaft is cut down to install a yoke that fits the shaft. Known as Hack-N-Tap.
http://www.ironrockoffroad.com/Merch...tegory_Code=UP

 

There are 3 ways to address the issue.
1st is a Slip Yoke Eliminator. You can buy a kit from vendors on here that includes a new output shaft and a yoke. This can be paired with a stock front driveshaft in the rear in most cases.
2nd is a Hack and Tap SYE that is mentioned above. Same idea, except you cut down the existing output shaft and tap it for a new yoke.
3rd is a transfer case drop. Inserting spacers between the frame and trans cross member. This will lower your t case angle to make it more appropriate for a Slip Yoke. This is more of a band aid, very cheap, but can cause issues if you have worn motor mounts.

I would recommend the 1st option. Very easy to do. 2nd is a little cheaper, and many have used this method with success.
It could also be bad u joints, so check that first, but your angles will likely need to be addressed.

 

I put a similar lift on my 96. Did option one. Solved all the problems. Also I invested in new drive lines front and rear. Do it sooner than later, or you will be spending some real coin on a differential rebuild. I know from experience. The vibes will destroy the pinion bearing races and other stuff. Fix the angles now, or save up $1300 for diff repair.