I have a rear end for sale and somebody asked if it's a 7.5" or 8". What am I measuring? Can I determine this without cracking the differential cover?
I believe the 7.5, the 8.2, and the 8.5 10 bolts all used different covers. You might look at the Richmond gear catalog/website to see what they look like. Larry T
The 7.5 and 7.85 were the small ones used in Camaros, 80s Monte Carlos and S-10s, very small cover and tubes. The 8.2 was used between I believe 64-72(early) and 73-81(later) and the 8.5 is a newer design I think, other oppinions ??
Cover shapes----7.5 looks like a circle with squared off corners, 8.2 looks like a circle with a concave cutout on each side, and 8.5 just looks like a circle.
There were also a couple of different 8.2 10 bolts. The "standard" Chevrolet type, a different BOP style, and even a 10 bolt ring gear type with a 12 bolt cover. Makes things real interesting sometimes. Larry T
Take a look here, it'll clear things up---------or even muddy the waters more. Larry T http://www.richmondgear.com/01gm.html
The BOP are Borg Warner and thier 10 and 12 bolt version both had a odd 10 bolt cover, semi-circle with cutouts on each side.
As I wouldn't even consider buying a ten bolt without pulling the cover, why don't you pop the cover off of it, measure the ring gear and make sure that the rear end is in first rate shape before you sell it. I've looked at too many of them where the pin that holds the spiders in is loose in the housing. That will let you know what gear ratio you have too and that could make a big difference in price as some are a lot more popular than others.
I found Larry's link a while back when I was researching gears. My rear end came out of a 72 Nova and is a Posi. That's all I know. The gasket pattern looks like both: http://www.richmondgear.com/07pdfs/RG10.pdf and http://www.richmondgear.com/07pdfs/RG13.pdf And both have Nova in the criteria......doh! So without measuring the ring gear I guess I still don't know what I've got.
If you'll pop the cover and look, the 8.2 uses 3/8 standard bolts on the ring gear. The 8.5 uses larger metric left handed bolts (at least I think all of them do). OK. Just looked at the link and that's gotta be right. Larry T
I don't know, but I looked at the replacement gears and they are the same for 70-96 8.5 rearends. I know the newer 8.5s are Metric left hand threads. Larry T Looks like I'm wrong again(not the first time, won't be the last). Mr. Gasket lists them like this: GM 10-Bolt, 8.5'' ring gear (ex. O axle), 7/16''-20 x 7/8'' LH, 10/pkg Stock Length Ring Gear Bolts Scuze me while I go look at a couple of rearends I have torn apart in the shop. OK, went and looked, the stock lefthanded bolts have a M in the middle. I always assumed for metric, 19MM socket fits them but so does a 3/4". Never too old to learn.
Oh...and if you convert 3/4" you get 19.05mm....which would explain why a 19mm socket will work on a 3/4" bolt head....only 0.05mm difference.