Ring and pinion gear id, 64 Posi

[John R.]

64 differential has the following stamped numbers:

Ring, OA 3756448 12:37 GM 3 67
Pinion, 3819184 GM 1 12:67 12:37

Assembly stamp on differential is CB 5 7 64 with AB on the other side, and casting date of C94.

Has a Dana Posi with the following:

Casting date: 30, guess julian date of Jan 30th
Stamp on unit is: C 32324 and C21064
Has a large 24 cast into the side along with PAT 2966076

Is this a 3:08 or 3:36??

[Joe L.]

Re: Ring and pinion gear id, 64 Posi

64 differential has the following stamped numbers:

Ring, OA 3756448 12:37 GM 3 67
Pinion, 3819184 GM 1 12:67 12:37

Assembly stamp on differential is CB 5 7 64 with AB on the other side, and casting date of C94.

Has a Dana Posi with the following:

Casting date: 30, guess julian date of Jan 30th
Stamp on unit is: C 32324 and C21064
Has a large 24 cast into the side along with PAT 2966076

Is this a 3:08 or 3:36??

John------


It's a 3.08:1 ratio used for 1963-64 Corvettes. The gearset was known as GM #3822991.

[Chuck G.]

Re: Ring and pinion gear id, 64 Posi

The 12:37 stamped on both items is the giveaway.

37/12 = 3.08

You'll find similar ratio stamps on all Corvette rear gears (ring and pinion)

Chuck

[John R.]

Re: Ring and pinion gear id, 64 Posi

So, the CB denotes 3.36, but the gears have been replaced to convert to 3.08??

[Larry M.]

Re: Ring and pinion gear id, 64 Posi

The 12:37 stamped on both items is the giveaway.

37/12 = 3.08

You'll find similar ratio stamps on all Corvette rear gears (ring and pinion)

Chuck

Or just COUNT the teeth and then divide. Works every time.

Larry

[Wayne M.]

Re: Ring and pinion gear id, 64 Posi

...It's a 3.08:1 ratio used for 1963-64 Corvettes. The gearset was known as GM #3822991.

And the original 3.36's (CB code) were changed to the 3.08's sometime after 12-67 (the latest stamped date, which is on the pinion, in your situation). I don't know enough about Dana posi cases to guess at whether it was also changed, along with the R & P. The Dana 3 and 4-series positraction cases were definitely still available from GM at that time.

[Chuck G.]

Re: Ring and pinion gear id, 64 Posi

Gears get switched in cases all the time.

I have the entire original 4.11 rear pumpkin from my 63 on the shelf.

In the car is a 3.08 case, stamped CJ I believe. Don't remember the date sometime in 1963, but in that case is a set of 3.55 gears.

I still have the original pumpkin in my 69. It was a 3.08, but when I rebuilt it, I put in 3.36 gears.

Chuck