Original rear end?

[William S.]

I have what is supposed to be a numbers matching 66 427/390 4sp car that NCRS shows a build date of 11/02/65, engine and trans numbers all check out, but the rear says FB 10-25-65. Is it possible that it was a special request from the dealer to be ordered with the 4:11 or changed at the dealership? or was it more likely just swapped out at some point? It just seems odd that the date would be so correct for someone to just acquire a FB rear with a date that would line up with the actual build date of the car. Not impossible I know, especially if it was done back in 1966. Just trying to validate my car as much as possible.
thanks.

[Mike T.]

Re: Original rear end?

William - How long have you owned your 66? If it's only been a short while, then maybe it's more likely that someone made the swap but if you've had it since the 70's or 80's, I'd say it's less likely anyone worried about getting all the parts dates to line up meaning it was more likely special ordered that way or as you mentioned, maybe they had the dealer do the deed. Not exactly the same thing but when my ex-Father in Law ordered his new '70 Z-28, he had the dealer swap the 4:11's for 3:31's since he intended on some highway driving. This took place shortly after buying it.

[Dan A.]

Re: Original rear end?

The L36 with M20 came standard with 3.08 and the 3.36 was optional.


The L36 with M21 came standard with 3.36. The 3.08, 3.70, 3.55 were optional. 4.11 was not availeable with the L36.

4.11 was optional with M21 equiped L72. M20 was not available with the L72.

[William S.]

Re: Original rear end?

We have only owned it for about a year. That's why we're trying to research this car further.

[William S.]

Re: Original rear end?

The L36 with M20 came standard with 3.08 and the 3.36 was optional.


The L36 with M21 came standard with 3.36. The 3.08, 3.70, 3.55 were optional. 4.11 was not availeable with the L36.

4.11 was optional with M21 equiped L72. M20 was not available with the L72.

That's what we've found out, which is why I'm trying to figure out if it was possible it was a dealer swap or just a owner who did it at some point. The odd thing is the rear end date shows 10-25-65 AND the date code on the tranny is P1025. That seems odd that they would match like that if it was someone who just changed it for some reason. Any opinions?

[Ronald L.]

Re: Original rear end?

Previous owner hunted for a short while and found a dated rear end not knowing it was not a 390HP option.

[Tim G.]

Re: Original rear end?

Have you actually checked the gear set by lifting the car and rotating the wheel? I wouldn't think they would install the wrong gears in the case, but you never really know what gear ratio is actually in the case.

[William S.]

Re: Original rear end?

Have you actually checked the gear set by lifting the car and rotating the wheel? I wouldn't think they would install the wrong gears in the case, but you never really know what gear ratio is actually in the case.

That's a good point. We couldn't check the last time it was on a lift because it was a drive-on lift. But something that I will definatly be doing.

[Joseph T.]

Re: Original rear end?

William.
Do you have the Warranty Book (POP) ? The rear end code and date are listed on the plate in the back of the book.

[William S.]

Re: Original rear end?

William.
Do you have the Warranty Book (POP) ? The rear end code and date are listed on the plate in the back of the book.

unfortunatly no, long gone i guess.