Todd, I've installed a set of 4:11 gears in my 3600 and it's great. I thought about the T-5 but I was concerned that it was a bit of a light weight for the 3/4 ton. But, what I learned, and was a total surprize to me, is that the 4:11s were the right decision in that with this ratio at the rear end the truck is so much better thoughout all the gears. Where as the T-5 would only be an improvement once in od/5th gear. Best of luck
