View Full Version : rear axle info

11-13-10, 04:34 PM
Howdy, this is my first post on the site. I have a '78 coupe deville that was wrecked, so I pulled the entire drive train out and put in in a 1951 GMC truck. The 425 runs great and the th400 is fine. The car only had 76,000 miles on it. Does anyone know anything about the rear axles in these cars? It has a 10 bolt rear cover with the scalloped sides like a BOP rear axle, but it appears to have a bigger ring gear than the old 8.2 inch axles. The reason I am asking is because the axle has a 2.28 to 1 gear ratio which was great for freeway cruising in the caddy, but sucks for trying to haul anything in a truck. I want to change out to a steeper gear ratio and maybe a posi, but need to know if this axle is worth upgrading or if I should start looking for something else. I havent been able to find out anything about these axles so any info/advice would be appreciated. Thanks!

11-13-10, 08:11 PM
When I was looking to upgrade one I had, I couldn't find any gears to buy, only a posi unit. But, when I asked a shop to do it, they looked in their computer and said they could put other gears in. So I don't know if they had the wrong info or not but I couldn't find any gears to buy either.

11-13-10, 11:24 PM
Yeah, maybe thats the answer. I'll call a shop and see if they have any info. Sometimes they have stuff through their suppliers that you cant find on your own.

11-14-10, 10:43 AM
It's an 8.75 ring gear. there was a guy a few weeks ago selling gears and lockers for those rear ends on ebay.

11-14-10, 06:44 PM
This is the guy:

http://cgi.ebay.com/ebaymotors/GM-8-75-3-42-GEARS-342-BUICK-PONTIAC-OLDS-10-12-BOLT-_W0QQcmdZViewItemQQhashZitem23097e4971QQitemZ15048 3126641QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccesso ries

11-18-10, 02:53 AM
Thanks for the info. That guy has a bunch of good stuff and now I know what to look for