I'm considering purchasing a GS455 that has a GM Corporate 8.5 with 3.08 posi gears. I notice that Richmond Gear has 3.42 ring and pinion sets that will bolt right in but, they show it with two carriers, a 2 series and a 3 series. So, is there a way that I can know if the carrier that's in the rear now is a 2 or 3 series or, do I have to take the cover off? If so, how do it tell, then?
Ray, the carrier breaks for the GM 8.5 10 bolt are 2.56 and down and 2.73 and up, so if the rear has a 3.08, it will accept the 3.42's or 3.73's. https://www.crawlpedia.com/thick_gears.htm (Just scroll down for the chart)
8.2 rear 2.93 gear were available for 1970, so probably 3.08 gears were available for a 8.5 rear for 1971.
If it is the original carrier and 3:08 gears then the 3:42’s will go right in. I would suggest a Motive Gear or US Gear. Richmonds can be very finicky to the novice installer.
Below is a pic of the axle which the seller tells me is a '71 or 72 Corporate 8.5 10 bolt. I guess I misread the catalog from Richmond Gear. I understand that if it has an 8.5 10 bolt with 3.08 gears now that the 3.42 will bolt right in.
That's an 8.5. You can see the squared off lugs on the bottom at 5 and 7:00. I don't know about the sway bar, but it doesn't look right. I know the cover from a GN would fit, maybe the sway bar as well?
That's what I was hoping. Locks up fine and not noisy at all. Thanks, Bruno and Larry. Also, tachs about 2800 RPM at 60 MPH so, should be a 3.42 or maybe a 3.55. Seller doesn't know for sure.
LOL! And I don't even have the car yet. That was the seller's pic to show me the posi was working right. We just agreed on the price last night and I'm working on having it trucked down here from up in the midwest. Looking forward to it.
