1963 rear end code

[Larry Ruben]

I have an early '63 and the rear end code reads AP W089 E1. Can anyone shed some light on this? Noland are you out there? If I assume the 1 means 1961 then the AP corresponds to 4:11 positraction. Did they make independent suspension rear ends in 1961 for some other purpose since the solid axles were used through the '62 model year?
Any help would be appreciated.

[Joe L.]

Re: 1963 rear end code

Larry-----

The "AP" code was used for 1961 but, I assure you, they weren't making the 63+ style differential units for PRODUCTION at that time. Also, no other car ever used the Corvette-style IRS differential assembly.

Although the "AP" code was not used for 1963 or 64, it was used for 1965 through 1969 for 4.11:1 positraction with small block. I think that's what you have here and, apparently, someone swapped in a 65-69 unit at some point. As an assembly, these are completely interchangeable with the 63 units. I can't completely decode the sequence you have, but the "W" represents the Chevrolet Warren Gear and Axle Plant where the unit was assembled. The "E" denotes an Eaton positraction unit, which all 65-79 Corvette differential assemblies used.

For the most part, the date coding is moot since it's not a 63 assembly and could not be original to the car.

[Larry Ruben]

Re: 1963 rear end code

Joe, thanks for your response, but I believe the rear end to be original. I have full documentation with the car and there is no indication of a rear end swap. If it were a '65 it would have a 5 as the last digit and probably would not have a W as part of the date code. I realize that IRS wasn't installed until the '63 model year (which would start with a June or July '62 date). My question is did they develop this rear end in 1961 or earlier and somehow one of these earlier ones wound up in my car on the production line in Oct. 1962.

[John H.]

Re: 1963 rear end code

Larry -

What's the casting number and date?

[Joe L.]

Re: 1963 rear end code

Larry------

I'm sure that the IRS Corvette differential was developed well before 1962 and, likely, well before 1961. However, at these early stages, the differential units would generally have been prototype pieces, would have differed from PRODUCTION pieces in certain ways, may have had "X" suffixed casting numbers (or no casting numbers, at all) and it's VERY unlikely that one of them would have found its way into a PRODUCTION car. Of course, just about anything is theoretically possible.

Also, the "W" would have been present in your carrier ID series inasmuch as I believe that ALL of the assemblies from 1963 to 1979 were manufactured at the Warren Gear and Axle Plant. Some MAY have been manufactured at Chevrolet-Buffalo, though. The "E" in the series indicates an Eaton positraction unit. These were not originally used for 1963 Corvettes.

What is the casting number and casting date of your carrier housing and carrier cover? That information might be useful in getting to the bottom of this.