Hello, can someone tell me or point me in the right direction for rear end codes for a 1971 GS 455. The car came with a 12 bolt and 10 bolt 8.5. For one of these to be factory, what codes should be on them? What should be on the 12 bolt for a code that came with a Canadian built 455 auto GS? Thanks guys
??? Welll I heard on this site the 71 72 did not have 12 bolts...??? Even in Canada...BUT as that goes and as I have personally seen DOES NOT ALWAYS work or is correct. So 12 bolt chevy codes are on the passenger side facing forward and will usually be a 2 letter code and other number beyond that for date and plant info. The Buick 71 72 code will be on the driver side tube between the spring perch and cast center. Jim
I have seen 12 bolt rears in 70-72 Skylarks up here in Canada, I am not positive they were factory though and I never looked for the codes.
Have a look on page 25 of this pdf http://www.buick-riviera.com/servicemanual/040-55-83.pdf The axle codes are listed. I believe the correct rear will be the 8.5 10 bolt, and IMHO, I'd prefer that to the 12 bolt rear as it will be bolt in axle, almost as strong, and cheaper to build up. Plenty of aftermarket support for the 8.5. Make sure the 10 bolt you have is an 8.5 and not an 8.2. The 1971 GS had an 8.5, but it sounds like you aren't sure what you have. Do you know how to tell the difference?
'68, '69 & '70 were available with 12 bolt rears in Canada. GM Parts Book refers to them as "Chev. Type Axles" with 12 bolt holes.
So according to that PDF the code should be on the passenger side top of diff correct? The 10 bolt I have is the 8.5 but for some reason can't find the code. So, if a 71 didn't come with a 12 bolt a guy is better off with the 8.5 10 bolt is what iam kind off hearing?
That 8.5 10 bolt is a very stout rear. It has bolt in axles. The 12 bolt will be C clip. The 8.5 has the same pinion support, and pinion shaft diameter as the 12 bolt. You can upgrade the 8.5 to 30 spline axles, and 30 spline Eaton Posi, as I did, if you like. IMHO, you are better off with the 8.5
That's sounds good Larry thank you. However, I can't find the code on it but have the casting numbers (1382799) and (A30). How do I find out if that's a correct casting number for a 71 Buick?
Monzaz might be able to help, but why do you care about casting numbers, as long as it is a Buick 8.5?
Without finding the code on it from that PDF manual, should one assume it's the one that's supposed to be in there? Factory unit?
If it has the lugs on the bottom of the case, and it has bolt in axles, and the rear U-joint is held in by cap screws and straps, it's a Buick 8.5. Take the cover off, and read the numbers on the ring gear. Divide the smaller number into the larger, and you'll have the ratio.
