Originally Posted by Truckrolet
Originally Posted by red58
the 4.11 may not be listed, because it was not a separate option but paired with the OD 3 speed trans, which was available from 55.2 on .... '58 was the beginning of a variety of optional rear offerings, and AFAIK the first year for the posi, but the 3.9 was still "standard" and any of the others would be a rare find nowadays, I've searched for years but never found a posi and the only 3.38 gears I've seen were NORS at a rear end specialty shop or the the current new production from Patrick

Bill

I got one, but its more of a limited slip,has some clutch plates backing the differential side gears kinda like where the thrust bearings are. And its in an old style rear axle, like the 57's had. Hmm I guess that is what 58's used, 59 has a newer spread case design.
'59 was the first year for the Positraction rear, which used the GMC Spicer 45 housing. It was a 1 year only for Chevrolet. If you have a Eaton HO33 with a Positraction using, it most likely originally came out of a '60-'62. The Positraction, or "Posi", isn't "more of a limited slip", it is a limited slip. Positraction was just the Chevrolet brand name for it. Other companies sold virtually identical limited slips under their own brand names, such as Sure-Grip (Chrysler), Powr-Lok (GMC),and Traction-Lok (Ford).

Bill Burmeister