What is the best way to determine if my driveshaft is worn? The rubber part on the center bearing is cracked on one side and when i push up on the drive shaft from under neath, the driveshaft lifts up a few inches. Is this normal?

 

I forgot to mention that I have a 91 King cab sr5 4x4 with a 3" lift and 2" body on 35's. 5.29 gearing.

 

no that is not normal, sounds like you need a new bearing and insulator (rubber part) and possibly u-joints