[jonnyrot10]

Hey guys I am getting what sounds like a mix of grinding and vibrating noise coming from my transmission or rear end(maybe). It seems to happen when I am in 5th or 6th gear and decelerating from higher speeds. My guess is that is is my rear drive shaft(which is a stock rubicon shaft) causing the noise. My jeep only has 4500 miles on it, 1200 of those with the lift. I have 2.5" o.m.e. lift and a teraflex belly-up skid along with rusty's fixed lower control arms and adjustable upper arms. I also have a 1" body and motor lift. I have plans of replacing the drive shaft with a cv drive shaft(tom woods or coates do to this forum's recomendations) but hoping that you guys might be able to tell me if the sound i quite badly described sounds like a drive shaft and not some other problem. For it is that sound I am hoping to cure with the drive shaft.

[Jerky bump]

The only other thing I can think of is backlash noise from the gearing, but that's kind of reaching. I'm not sure how much pinion angle would affect them. You're guess would have been my first guess. Out of chance, the shaft isn't getting on the short or long side is it?

[rjt36]

I'm thinking it's got to be driveshaft related. You're essentially running a 3.5" lift because of the belly up. It raises the transfer case even higher than the 2.5" from the OME. It's probably from the driveshaft operating at higher angles.

You might also want to check your pinion angle. It's supposed to be 1 degree less than the driveshaft angle. I forget which is which, but if it's too high, you'll get vibrations during acceleration and if it's too low it will vibe during deceleration.....or vice-versa, I can't recall.

Either way, checking the pinion angle and looking into a CV shaft would be the first things I'd do.