Rear Diff Gear Whine - 07 Off Road AT
Hey all, I've got an 07 Off Road automatic with 119k miles. It's got some pretty loud high-pitched gear whine at highway speeds (40+ mph) and searching through the forums have left me more confused than not. Some people seem to say it's normal from wear and tear, others say the diff is about to explode. I have the service history for the car and the pinion seal and bearing were replaced about a year ago (with OEM nissan parts, but at a local shop, not a dealership) but I have no way to know if this whine persisted before that repair. My guess is if it's because of this, they didn't torque the pinion nut properly and screwed up the pinion bearing pre-load causing the gears to not mesh perfectly together; or it was unnecessarily repaired and a misdiagnosis. The other option is it's just like that because it's getting old.
I haven't checked the diff fluid yet, but I plan on replacing it with a heavier 75W140 to see if that helps and also see if there's an excessive amount of metal flakes in the fluid.
If they did just mess up the pinion bearing pre-load, I need to replace the just the bearing race? or the whole setup? What's a rough ballpark for DIY vs doing it at a shop for this?
If the ring and pinion and on their way out, should I look for a used rear end for an Off Road, or see if it makes more sense to get the diff rebuilt?
Or should I just leave it and turn my music up?