Differential Code Stamp
Thread Starter
Drifting
Joined: Aug 2010
Posts: 1,797
Likes: 304
From: Charlotte Area North Carolina
Differential Code Stamp
In the process of trying to document some numbers on a '66 Vette. I have the '66 Technical Manual and Judging Guide. According to the Manual my differential should have a casting number of 3871375 but it does not have this number on it or I'm not looking in the right place.
My differential has the following numbers on the back of it: K987 and 464910 with an "M" located under the 464910 on the back of the differential.
Bottom of the differential is stamped 11 4 65 but I do not see a two letter stamp indentifying the ratio, like AK, AL, AM that the Manual says should preceed this assembly date. This particular Vette is a 327 / 350 hp. Because I'm not able to locate the 2 letter code, I also haven't been able to determine if it is positraction or standard without taking it out on the street and lighting up the tires.
Is there another spot where I can locate the rear axle ratio?
My differential has the following numbers on the back of it: K987 and 464910 with an "M" located under the 464910 on the back of the differential.
Bottom of the differential is stamped 11 4 65 but I do not see a two letter stamp indentifying the ratio, like AK, AL, AM that the Manual says should preceed this assembly date. This particular Vette is a 327 / 350 hp. Because I'm not able to locate the 2 letter code, I also haven't been able to determine if it is positraction or standard without taking it out on the street and lighting up the tires.
Is there another spot where I can locate the rear axle ratio?
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
Two separate parts are involved - the differential housing (front part) and the rear cover (which the spring attaches to).
The differential housing casting number for a '66 is 3876476-N, which is located on the passenger side, just above the horizontal "fin" in the casting; the casting date is on the driver's side, partially obscured by the camber strut rod bracket.
The rear cover casting number is at the very top in the rear view, where the casting butts up against the diff crossmember; it's 3871375 for a '66. If yours shows 464910, the rear cover is from a '78 or '79, which uses 7/16" spring retaining plate bolts and a 2-1/4"-wide rear spring ('63-'77 used 9/16" bolts with a 2"-wide spring).
The 2-letter ratio code is stamped on the same rough as-cast surface on the bottom of the housing as the assembly date - clean it up and keep looking for it.
The differential housing casting number for a '66 is 3876476-N, which is located on the passenger side, just above the horizontal "fin" in the casting; the casting date is on the driver's side, partially obscured by the camber strut rod bracket.
The rear cover casting number is at the very top in the rear view, where the casting butts up against the diff crossmember; it's 3871375 for a '66. If yours shows 464910, the rear cover is from a '78 or '79, which uses 7/16" spring retaining plate bolts and a 2-1/4"-wide rear spring ('63-'77 used 9/16" bolts with a 2"-wide spring).
The 2-letter ratio code is stamped on the same rough as-cast surface on the bottom of the housing as the assembly date - clean it up and keep looking for it.
Thread Starter
Drifting
Joined: Aug 2010
Posts: 1,797
Likes: 304
From: Charlotte Area North Carolina
Thank you very much for the information and photos for reference. Undercarriage has been painted a few times and it's really hard to locate some of the numbers but your pictures are a big help. Thanks again.
I have located several parts, like rear Goodwrench Gas Absorber shocks that are from 1978. Story on this car is starting to come together and is looking more and more like it was rebuilt in 1978.
I have located several parts, like rear Goodwrench Gas Absorber shocks that are from 1978. Story on this car is starting to come together and is looking more and more like it was rebuilt in 1978.
