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Can you just have the gears tempered to get them a little less hard? Has anyone measured the hardness on each type?



Yes you can but it can be expensive to do correctly. It was a trick stock racers did years ago.

I had a set done probably late 80's or early 90's. I may have the original and after hardness somewhere, but I will have to look for it.

The trick is that you need to harden the surfaces after tempering or else you have excessive wear.

The outfit I had do mine did some sort of spray to surface harden the teeth. It was not very effective. After 75 runs, I inspected the gears had almost 100% tooth contact and the gears deformed to the point that the edges of the gears rolled over.

I was cheap and cleaned the edges up and ran it for many years and many runs that way. Never got worse. Sold the rear end about 12 years ago - it never failed on me.

My metallurgist says that what should of been done after the gears were softened is the root of the gears should of been masked and then the teeth hardened by carburizing.

67 Coronet 500 9.610 @ 139.20 mph
67 Coronet 500 (street car) 14.82 @ 94 mph
69 GTX (clone) - build in progress......