Differential Casting Numbers

[Robert E.]

Hi,

I've known for some time that the differential in my '71 LT-1 was changed. It was recently confirmed by a previous owner that had it done.

I have a line on a correctly dated case and was wondering if there are different casting numbers used in '71. One for HD applications (big block and LT-1) and small block applications?

I apologize in advance if I've used incorrect terminology, but I'm sure my question is understandable.

Thanks

Robert

[Lynn H.]

Re: Differential Casting Numbers

Robert,
I believe the CASTING number on the differential case (housing) would be the same, but the ASSEMBLY would have had a different part number, due to the different yokes installed. The manner in which the half shafts are attached to the yokes are different (caps w/ bolts versus U bolts and nuts). What may be of more importance to you would be the code stamped on the case (unless you are thinking of restamping). You would need to consult the pocket spec guide or the judging manual for the correct code to correspond to your gear ratio, with the heavy duty application.
Lynn

[Robert E.]

Re: Differential Casting Numbers

Lynn, Thanks for your response. The case I found has the correct cast date but not the correct ratio stamped that I require. I'll more than likely keep the stamp as is and build the diff for my application. Do you or anyone else know what the casting part number should be? I like to be armed with as much information as I can before making an offer for it. Any additional information would be appreciated.

Robert

Robert,
I believe the CASTING number on the differential case (housing) would be the same, but the ASSEMBLY would have had a different part number, due to the different yokes installed. The manner in which the half shafts are attached to the yokes are different (caps w/ bolts versus U bolts and nuts). What may be of more importance to you would be the code stamped on the case (unless you are thinking of restamping). You would need to consult the pocket spec guide or the judging manual for the correct code to correspond to your gear ratio, with the heavy duty application.
Lynn

[John H.]

Re: Differential Casting Numbers

Do you or anyone else know what the casting part number should be? I like to be armed with as much information as I can before making an offer for it. Any additional information would be appreciated.

Robert

Robert -

The casting number for the differential housing is 3899143; the casting date is on the driver's side, partially obscured by the camber strut bracket.

[Wayne M.]

Re: Differential Casting Numbers

...The case I found has the correct cast date but not the correct ratio stamped that I require. I'll more than likely keep the stamp as is and build the diff for my application. Do you or anyone else know what the casting part number should be? I like to be armed with as much information as I can before making an offer for it. ....

Robert -- here's the castings and stamping on an early '69 (originally 3.08 posi, now a 4.11 posi case inside). The carrier is cast I_11_8 (Sept 11th) [no pic], and assembled Oct 22nd 1968. The carrier part casting # is 3899143, which I believe is the number you should be looking for.

[Joe L.]

Re: Differential Casting Numbers

Robert -

The casting number for the differential housing is 3899143; the casting date is on the driver's side, partially obscured by the camber strut bracket.

John and Robert-----


Yup, that's the number and there are lots of them out there (although not necessarily with the date code you're looking for). The 3899143 was used from 1967 all the way through 1979 for all Corvette applications.

[Robert E.]

Re: Differential Casting Numbers

Gentlemen, Thank you so very much. I sincerely appreciate your assistance

Robert

John and Robert-----


Yup, that's the number and there are lots of them out there (although not necessarily with the date code you're looking for). The 3899143 was used from 1967 all the way through 1979 for all Corvette applications.