I've had a 69 Z for about a year. The rear end is making the grinding noise when i come off the gas. It actually has the rear out of an 83 camaro....7.5 gear, 10 bolt....really puny but it is a good setup with the tranny and 350. I think it has 3.73 gears and posi but i'm going to check. It does 3200 rpm at 65 with 27" tires and 350 eng. I don't do a lot of highway driving and i don't really want to change out the whole rear end. It is difficult to turn over the tires from a stop. It is an auto with a B&M. How can i get more power from a complete stop? I think the 3.73 is a good mid-range gear. Am i correct? Should i put a 3.73 back in it and try to find a better manufacturer or should i consider changing out the whole rear end? Or should i try a different ratio? I currently get 10 mpg but that is not important to me otherwise i would have bought a 4 cyl. Any suggestions??