Thin P, Fat P

[David H.]

In my quest for a date correct rear axle for my brother's '62, I have come across a case only that is dated correctly. However, the seller refers to "THE LARGE "P" BY THE PART NUMBER WHICH INDICATES POSI-TRATION. IT HAS THE THIN "P" SO IT IS A FLINT CASE AND COULD HAVE BEEN USED ON A CORVETTE OR FULL SIZE CHEVROLET.

What exactly does this mean? Was there a "Fat P" that meant something else? Is the correct rear axle for this car Corvette only? Or were they used for other Chevrolets of the time?

Attached mine.

Thanks

[Clem Z.]

Re: Thin P, Fat P

i am glad i read the whole post because from the title i figured you were talking about prostate problems.

[John H.]

Re: Thin P, Fat P

What exactly does this mean? Was there a "Fat P" that meant something else? Is the correct rear axle for this car Corvette only? Or were they used for other Chevrolets of the time?

Attached mine.

Thanks

David -

All Corvette rear axles came from the Detroit Gear & Axle plant, which also made passenger car axles; all their diff castings came from Saginaw, and the Positraction diff housings from Saginaw had the "thin" P (like the one in your photo). Passenger car rear axles were also made at Buffalo, and their Positraction diff castings used a "thick" P; none of those diffs went into Corvettes.

Photos below of "thin" P and "thick" P diff housings.

[David H.]

Re: Thin P, Fat P

Thanks John,
Great info for me.
So if the one I am looking at for sale has the thin P, it definately has to be a Corvette rear case. It has a THE CASE IS DATED H311 [ AUGUST 31ST 1961 ] . I dont know that I want to swap just the case tho. I would rather replace the entire assembly with a date correct posi unit.
Your thoughts on this?

p.s. My prostate is a-ok!

[Dan A.]

Re: Thin P, Fat P

So if the one I am looking at for sale has the thin P, it definately has to be a Corvette rear case.

No. Re- read Johns post.

As John said the Saginaw thin P cases were also used in passenger cars.

There is a an assembly date and application code stamped in the passenger side of the face of the case that defines the useage. Passenger car codes differed from Corvette codes. It will have to have a thin P and a Corvette code to be from a Corvette originally.

[David H.]

Re: Thin P, Fat P

Well, this case has AX905 stamped in it on the passengers side. I dont see that listed anywhere in anything I have on Corvettes. It must be a passenger car code? What is the 905?

[Dan A.]

Re: Thin P, Fat P

this case has AX905 stamped in it on the passengers side. It must be a passenger car code? What is the 905?

AX905, AX deignates a 3.08 posi from a passenger car that was final machined and assembled at Detroit Gear on 905 or September 5th. The housing was cast F71 or June 7/61 which proceeds the September build date.