Hey I wanted to chime in here as I have quite a bit of experience on the subject as I had mine rebuilt 3 times. 1st time was not a complete rebuild and lasted ~40,000 KM. 2nd was a complete rebuild and lasted less then 10K. My mechanic never put any additive into the diff so it blew out mighty fast. I took it back to him, instead of making me pay the $1200 again, he did it for parts plus a bit of labor ($500)... This lasted and was quiet until I scrapped it, another 15,000KM's.. Previous post could certainly be correct as the housing is probably out of spec, causing bearings to fail prematurely. However, usually when bearings go bad its a loud howling, rather then a grinding noise although they can/will go hand in hand when the rear end goes bad. To me it was more of a 'scraping' noise inside the cabin, with a lot of howling. Try taking it on the highway and see if it gets louder with speed, acceleration and deceleration. And yeah, check your brake pads, rotors, ebrakes too!!