Join Date: Jan 2015
Location: Injun Territory, 'Merica!
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 121 Post(s)
The only "Chevy" casting number rears installed in US built Pontiac musclecars were McKinnon plant built 12 bolts, used in factory '70-72 Pontiac 455 application A bodys as well as '70 GrandPrixs with 400 4spds. The center housing casting numbers on these were 3969278, 3969278N, & 3969278NF. These exact same center casting numbers were ALSO used on same era ('70-72) 12 bolts cast out of two other GM axle plants, but those axle plants cast the center housing differently with a large casting date in the RH lwr webbing.
Early Pontiac A bodys all received PONTIAC 8.2 10 bolts.
PONTIAC 8.2 10 bolts had their own center housings, own style ring and pinion, own design carriers, and own axle tubes that flared out to accept Pontiac bolt in axles.
Chevrolet 8.2 10 bolt had their own round 10 bolt rear cover with a splash lip on it. Chevy 8.2 10 bolt rears axle tubes neck down on the ends, as the axles are are retained with c-clips inside the carrier sand do not have flared out axle tube ends. Chevy 8.2 10 bolts took their own style chevy 8.2 carrier and ring and pinion. The chevy 8.2 10bolt pinion gear has less splines and requires its own pinion flange which uses the small Spicer 1310 ujoint.
The only uses for c-clip axle Chevy 8.2 10 bolts in US production Pontiac chassis were:
-multileaf 8.2 Chevy 10 bolt in base 1970 Firebird
-mono leaf 8.2 Chevy 10 bolt installed in all production '71 Ventura II's.
If a '64-72 Pontiac A-body has a c-clip axle 8.2 Chevy A body (Malibu-Chevelle-Elco) rearend in it, someone other than the original assembly plant has installed that rearend in the car. It's that plain and simple. I've done it many times in Pontiac partscars in order to be able roll them around. Across the country, many folks over the years have been happy to find the early configuration A body rear they needed to get what had been a bolt-in axle A body going. Original rears often spun an axle bearing, the early ('64-early 66) length bolt in axles have often been hard to find and thus the early Malibu 8.2 rear that was avail for $50 made it under another Pontiac. Other than installing an adapter ujoint in the rear of the driveshaft, the 8.2 Chevy rear was cheap and easy fix, and worked for them. That is exactly how 8.2 Chevy rears end up under early Pontiac A bodys.
As a GM differential builder, I personally do not like the 8.2 Chevy rears, as the lack pinion support and have cclip axle retention. I seldom build them unless a customer asks me to. Chevrolet deemed the 8.2 Chevy cclip rears weak enough that when a '65-72 Chevy product had more than 275 gross HP and aprox 325 ft lbs of torque, a standard issue 12 bolt was used. Most of the stock 12 bolts Chevrolet used also had their own weaknesses... am straying from the original topic.
Hope this helps.