[locomotivebreath]

Just some thoughts on the quick performance 9 differential that I installed in my 68 GTO . It’s a really nice unit and great place to deal with. It shipped in 3 separate boxes - housing, center section and axles . I reused my stock drum brakes . You will almost certainly need a longer drive shaft - about 1.5” in my case and if you’ll want adjustable upper control arms as your pinion angle most likely change . Mine started out about 4.5 degrees down . I measured my drive line angles with a digital finder and confirmed things with the tremec app to dial it in . I followed their break in procedure and today put about 120 miles on it and the diff is dead quiet . I went with a 3.50 gear down from the 3.90 I had in the bop and it was a good choice. I really didn’t notice any loss of performance and feel like I have more use of the engines power band and use of each gear . I also installed a QA1 I” bar that goes around the back of the housing and it made a noticeable difference in oversteer from the 7/8 bar . It’s an economical swap but keep in mind the added coin for control arms and drive shaft .