I think that rear is Cadillac commercial chassis (hearse and limo, not Fleetwood) only, and has difficult to find bearings, obsolete seals and little if any aftermarket support. Appears they only offered a 3.15 gear ratio with or without posi. If any posi unit other than used works, Brian Trick or Jim (Monzas) will know. Patrick http://nationalhearse.net/forums/fo...-1970-1976-commercial-chassis-rear-axle-seals
It's a 9 3/8 rear only the axles and axle bearings and axle housing are different. 2.78 was the std ratio. With 3.23 for the tow package. 2.56,2.78,3.08,3.23,3.42,3.91 and the super rare 4.45 gears where used in various year cars from 66-70. The rear housing is unique to the Estate Wagon.The axle bearings and seals are used in 3/4 ton Kaiser Jeep truck and the Cadillac commercial chassis. So other gears and limited slip carriers are hidden away in Wildcats and Electra's and Rivieras. All 67-70 Riviera had 3.42 limited slip. The complete rear is different but the carrier and gears will bolt in your wagons housing.
I got 18.5 mpg at 70 mph driving. My wagon home from Colorado to Penn with the 2.78. I put a 3.42 in the car sure helped the car around town and I plan on towing a open car trailer. If I was just doing road trip on the interstates with no towing I would leave the 2.78 in
The axle bearings are the Timkin cone type vs sealed roller bearings used in Wildcats, Electra's and Riviera. I guess Buick was figuring on some heavy loads for the wagon application. Also the 70 Estate had coil springs, but when GM went to the clam shell wagons in 71 used leaf springs and 12 bolt chevy
Do you have any idea of what the application was for the rear coils? I cannot find a part number for the life of me. They are pigtail on both ends so it's not the same as other B-Bodies. Thanks for all the info!!
