I have two rear axles... '68 GS400 open with 2.93, and '68 skylark open with 2.56. I would like to install a 3.42 posi, preferably instead of the 2.56. Can someone tell me what size I need without disassembling the unit? Also, does it matter what year? I found a '70 3.42 8.5 not too far from my house. Thanks, Gil
Not sure what size you may need. GM basiclly put a 8.2 rear under your car but it might have been changed through the years or if GM got in a parts pinch they might have stuck a differnet rear in there. Would need to see to make a positive ID. Also with a "2" carrier you need to get the gears made for that rear( they where different with a "3" or "4" carrier. I think 2 carriers where 3.08 and numerically lower. 3 was 3.08 to 4.11. 4 was 3.90 on up. but this is depending on what is under your car. GM made B or P style 10 bolts(cone type posi). Olds used 12 bolt 8.3 clutch type posi. And chebby used 10 and 12 bolt cluth type posi. Depending on year!!!! That 70 rear sounds like a good rear to have (more parts avalibility) Check out summit and others for parts avalibility. Go to www.oldsmobility.com and click on rear ends he has alot of info there. Hope I didnt confuse you, Dave
