I have an 89 IROC w/ the stock 9 bolt Borg Warner Rear End. It has the stock 2.77 gears and I desperately want to change them. I would like to go w/ 4.10 or 4.56 but I cannot find anywhere that carries ring and pinion sets for the 9 bolt rear end. If anyone knows somewhere I can get them, please let me know. Thanks

 

try 9bolt.com or randy's ring and pinion

 

I had the same rear end in my ta. I was realy hyped when i saw it was a 9bolt posi with disc brakes. I pulled the cover off it when I bought it and "suprize!!!" 277s! That rear end will make an AWESOME boat anchor, it is otherwise useless in my opinion. Go to the tpis website, www.tpis.com. They sell a 373 gearset for the bw 9bolt, only problem is that it will only fit in a 9bolt carrier that was 323 to 373. I have been told those gears will not fit in my 277 9bolt. If you dont want to use it for a boat anchor you can save it to put back in your car when you sell it or put it in another car to sell it. Im stuck with a 373 posi 10 bolt wit drums now. Its not as strong but its much better. I paid $450 for this rear end newly rebuilt. I bought a summit differential support cover to make it stronger. I also saw summit sells c-clip eliminators for this rear end. These would be nice but I could not justify the extra $ and work. Good luck!