Ok so heres the deal lately i have an odd sound coming from what sounds to be right under my center box (can't pinpoint because of the echo effect our pop cans create) when I let off the gas. It a whining/grinding sound but goes away as soon as I give it even a little bit of skinny pedal. From searching I think it could be a pinion nut coming loose? Am I on the right track of finding the cause. If anyone has had this problem please let me know and how you fixed it. Also is there a way to check to see if it is loose without dropping the drive shaft? sorry for the long post its just driving me nuts!

 

also its a 90 with a 30 in front and a 35 in back

 

Transfer case is full, fluid in good shape?

 

You should be able to tell if the yoke is loose without removing the DS. Just yank on the yoke hard up and down, side to side and in and out (your slip joint should allow in and out movement). There should be no play at the yoke, if there is then your pinion bearings may be worn. I don't think the nuts ever loosen, unless they're reused several times (you should always replace the pinion nut with a new one after being removed).

If you have yoke movement you could try replacing the nut and torquing it to 175ft/lbs and see if it quiets down. If it quiets down then change the gear oil because there will be debris from the worn bearings in your gear oil.

 

I just checked about 2 weeks ago and all was well. I will check again today just to be positive.

 

could it be my pinion bearing going bad?

 

It sure could be. Check your u joints while you're down there