Can somone tell me more about replacing U Joints or bearings

 

Try reversing the bushings. There's a thicker one and thinner one. Some people put the thick one up top and thin one on the bottom and have no issues. If I recall, the instructions are actually wrong and you should install them in the opposite orientation that the instructions call for.

i would try that before considering u joints

 

Did you follow this DIY: https://www.myg37.com/forums/d-i-y-i...-bushings.html

There's a mention of marking the drive shaft so that it gets mounted back in the same manner that it was originally. There's also (around post #45) the orientation of the bushings and that they may be different than what's in the Whiteline Instructions.

 

In addtion to whats mentioned above, the official FSm procedure is to "Clock" the driveshaft at the yoke. mark the bolts as The Pope mentioned and rotate driveshaft one bolt over and test drive and continue rotating and test driving until there is no vibration.

If that doesn't work and you really want to get into the U Joints the procedure is the same for any u joint however depending on the year and version (the G uses at least three different driveshafts) you may need a pres to get the driveshaft apart. Consult the FSM for which one you have, you can usually tell by the type of yoke is on the diff (i.e. three bolt, four bolt or six bolt).

post up how you end up resolving the issue and good luck!