Last summer I had a guy who works out of his garage, work on my rear putting in a new posi and gears. After about a week I decided to take my car racing. Afterwards, I noticed a hum in the rear end while going down the road. So I took it back to him and he checked everything over and re-shimmed the gears, but the problem only persisted. So, does anybody know a good shop in the grand rapids surrounding area that is good at inspecting and setting gears in mild-performance rear ends?? I want to get it inspected because I think I may have fractured or broke the housing. If anybody knows someone please let me know asap, I really wanna get riding again.