Need help identifying rear end

[Bill Richards]

This is a rear end on a 1966 300HP automatic. The only numbers that I can find on it are stamped accross the very bottom, they are AT 126 66 RE. There are the letters GM cast into the passenger side, near the propeller shaft.
Thanks,
Willie

[Joe L.]

Re: Need help identifying rear end

Willie-----

The "AT" code would indicate a 3.08:1 axle ratio used with a 427 (HD axles with cap type u-joint retention). The date would seem to be December 6, 1966. Not all Corvette differentials are stamped with a year, but I've seen some that were. If that is the date, it's too late to have been the original unit installed on the car. It would have been used for a 1967 model.

Regardless of the coding on the case, that does not necessarily mean that the same gears are still inside. You would need to determine that empirically.

Out of curiousity, do the yoke axles currently installed in this unit have the cap-type u-joint retention (i.e. nodular iron caps with BOLTS to retain the u-joint caps) or do they use u-bolts (with nuts) to retain the u-joints?

[Bill Richards]

Re: Need help identifying rear end

Joe,
Thanks for your reply. Here is a good one, it has one of each, a non-nut one on the passanger side, and a brand new, u-bolt with nut type, on the drivers side. The non-nut one looks to be quite old. What do you think of that set-up?
Thanks,
Willie

[Joe L.]

Re: Need help identifying rear end

Wille-----

I'm sure there are more than a few of these out there. Of course, none originally came that way from Warren Gear and Axle. Apparently, someone replaced one of the axles and wasn't savvy enough to know that they were using a type which didn't match the other one. Or, they knew, but the non-HD was what they had, so they used it. That's the "get-it-back-on-the-road-and-out-the-door" philosophy of car repair. Replacing ONE axle is a bogus, slip-shod sort of thing, anyway. If you're in there to replace one, you might as well replace the other. Certainly, it will have some wear even if it's not beyond re-use.

The fact that the old (and, likely, original) axle is the HD type confirms the 1967 427 application for this unit as originally installed.

[John H.]

Re: Need help identifying rear end

It's also possible that the "1 26 66" is January 26, 1966; I've seen many '66-'67 diffs with the month expressed as a single digit rather than as two digits where the first one would be a zero. My '67 "AM" diff is also stamped "5 24 67", not with "05 24" or "05 24 67" some of the code books would tell you to expect.

[Bill Richards]

Re: Need help identifying rear end

Thanks guys,
After looking at it a little closer I determined that it is a 308 ratio, and positraction. Could of been a special order. Back in 69 I ordered a Z 28 and think i was able to choose my rear end ratio. 411 posi.
Willie