Mid Year Rear Pinion Seal

[Mark Hedberg]

The rear pinion seal on my '64 is leaking. The problem is I think the rear differential is from a later year. (I don't know exactly what year it is because the markings are gone, but there is a red tag on the filler hole.) Most of the catalogs list one seal for '63s and '64s, and another for '65 and up. My Corvette Parts Book lists only one seal (3924031) for years 63-72. Which is correct?

[Wayne W.]

Re: Mid Year Rear Pinion Seal

Probably both. The aftermarket and GM for that matter often superseeds parts with fits alls to reduce part number inventorys.

[Joe L.]

Re: Mid Year Rear Pinion Seal

Mark-----

I believe that there are different seals for 63-64 and 65-79. Both are still available from GM. The 63-64 seal is GM #464140 and the 65-79 seal is GM #3924031.

I believe that the reason for the difference relates to the fact that the pinion gear shaft configuration and the companion flange configuration is different for 63-64 and 65-79. As far as I know, the two are not interchangeable.

As far as which you have, your best bet is probably to remove the seal and match it up to one of the two above. That way, you'd be sure that you're using the correct one. Also, seals usually have a part number embossed on the metal portion of the seal. It is unlikely that it will be either of the two above-referenced numbers, but it will be cross-referenceable to one of the above.

As far as the red plastic differential posi tag goes, if it is ORIGINAL to your carrier assembly, then you have a 65-79 type unit. The red plastic tag began in 1965, although the script varies over the 65-79 period. 1963-64 units used a round, metal tag.

Although there are differences in the 63-64 and the 65-79 carrier ASSEMBLIES, 63-67 assemblies are interchangeable AS A UNIT and do not require any additional modifications. In order to be used in a 63-67, carrier assemblies originally installed in 68-70 Corvettes MAY need to have the companion flange changed if they were originally installed in an automatic-equipped car. All carrier assemblies originally used in 71-79 Corvettes WILL need to have the companion flange changed if they are installed in any 63-67 Corvette.