Hey Everyone,

I have a 96 XJ and it has recently started to get a vibration around 70 mph and has slowly become louder and more noticeable. It is definitely coming from the rear of the vehicle but I wasn't really able to determine where. I decided to put it up on jack stands and run it to see if I could video anything. Everything ran smoothly until I let off the gas quickly and then there was a terrible sound of grinding metal, clashing gears, or something like that. I didn't want to do it again since the sound was so awful. Does anyone know what this could be? Or what I should check next?

I recently replaced the u-joints and the oil in the diff.

 

Ever checked your transfer case and rearend fluid levels?

 

yeah, I changed both of those within the last two weeks.

 

With the vehicle's tires blocked and in Neutral, crawl under it and wiggle the driveshafts every direction you can.
Inspect the engine and trans mounts.

 

I was looking at the mount yesterday. The trans mount seems to lean quite a bit towards the passenger side of the vehicle. It concerned me! Does it normally lean in that direction?

The driver side engine mount has a crack in the rubber. I’m planning on replacing them.

I’m confused on how this would cause the gear grind (or whatever I heard in the rear of the vehicle after letting off the gas). Would that pull the everything forward and change the backlash in the diff?

 

Here.

Mount can be bad. The 2 bolts that hold the mount up could have fallen out. Motor mounts could be bad.

 

Dont forget to lube the slip splines on the driveshaft yoke up front