2000 xj 177k miles, has run very well, 3.5-inch lift with 31 inch new BFG AT tires it had a slight vibe 40-45 MPH (steering wheel vibrates but car really doesn't), tires were balanced and all-new (w/in last year) front end suspension with heavy duty parts. it has a stock rear drive shaft, no SYE, tried a TC drop, thought it put too-much stress on engine block, so removed TC drop. i then put 4-degree shims in rear leafs to get pinion angles perfect, they are now parallel with angle finder. my rear driveshaft was pointing upwards 4-degrees so i shimmed it and torqued everything to spec with new u bolts.

ever since i put rear shims in i get a god-awful grinding feeling and noise, but it is only when i take my foot off the gas, not ever during acceleration.

i can feel it underneath my seat and hear it in the rear, and am scared to drive it. i will change ujoints but they look very good and are smooth when i removed the rear driveshaft. i had limited slip with new gears put on 12-months ago and they have sounded and felt perfect except the other day when i put in the shims to correct my pinion.

any advice on what you think i am stressing with the new shims if my pinion is now perfect? thx, scott in NC.

 

Sounds like you have an SYE in your near future. I had the exact same thing about a week after lifting my '01. Every time I started coasting I had the grinding noise you describe. Installed the IRO HnT and some 4* shims and it went right away. Got my CV driveshaft for $45 from the junkyard

 

Before buying anything, make sure your pinion bolt is tight. I had the same problem when i got my XJ, acceleration was fine but deceleration down to about 15 mph i had a decent howl. When i checked my pinion bolt found that it was damn near hand tight. I tightened it up and was good to go.

 

If you only get vibes on deceleration, then your pinion is too low...........
Why did you feel the need to use shims with no SYE?
Did you have bad vibes before trying shims?

Typically you would want both yoke angles to match with a slip yoke, but keep in mind that your pinion will raise slightly under acceleration, and drop slightly on deceleration...............

I would try removing the shims, and see where you are at.......

 

thanks for the replies. i have tried 2-degree, 4-degree and 6-degree shims, what a waste of time and money, oh well. i even had my angles perfect and still got steering wheel vibes and play. still have vibes in front wheel between 40-45 mph and steering wheel bobbles laterally, but jeep doesn't, smooth as butter in all other speeds!!!! so perhaps its either wheels or steering but i doubt its steering as there is no play and its tight. i removed all shims and went back to what it was and the noise is gone from the rear, but i will still check the pinion bolt to be sure. i appreciate the help. scott

 

Front wobble could be a bent wheel, or out of balance..............
Wheel weights get knocked off from time to time.....