[Lawman_76]

Looking to put a set of gears and a posi in my '76 Bonneville, what cars can I get the carrier out of to do the swap? I also wonder if a 12 bolt chevy would fit since they are a bit stronger, My power level is projected to be around 400 horsepower and it is a heavy car so Im kinda weary about what the stock rearend can take.

[Lawman_76]

Looking to put a set of gears and a posi in my '76 Bonneville, what cars can I get the carrier out of to do the swap? I also wonder if a 12 bolt chevy would fit since they are a bit stronger, My power level is projected to be around 400 horsepower and it is a heavy car so Im kinda weary about what the stock rearend can take.

['ol Pinion head]

Lawman,
12 bolt Chevy rearend won't fit in such chassis. Neither 65-70 Impalla 12 bolt or either of the widths of the 12 bolt Chevelle housings will fit. If you had a wagon (leaf spring), yes, an Impalla housing could be modified to fit, by welding on leaf spring mounts.

Rearend ID on what you have...what you need to do is jack up the car, & look at the rear cover on the rearend. IF the cover is real deep & sticks out from the housing about 4"-5"s, you have a big car rearend that uses 8 7/8" big car gears...not 8 7/8" 12 bolt Chebby, not 8 7/8" 12 bolt pickup. Trust me on this, as this ring & pinion series is the same from 1971-1976, not avail aftermarket, & not avail in anything earlier or later... I can go to the Pontiac master parts books & break the ratios down further, if needed. In this style of gears, 3.42's were the lowest avail ratio & are near impossible to find used. 3.23's are tough to find as well. 3.08's are out there. This style ring gear will be held on by 12 small bolts, but the rear cover is held on by 10 bolts. Factory Eaton posi carriers are out there for these used (usually in high ratio form), however many often end up being put on e-Bay by the unscrupulous as 12 bolt Chevy carriers (NOT) & folks end up getting ripped off as they think they are buying something that will fit their 12 bolt Chevelle or Camaro. I can post links, if you like. These are a strong carrier, use same clutchs & better design (bigger spider gears) than stock 12 bolt. In comparison to a 12 bolt Chevy posi, the carrier is much longer from bearing to bearing & the side gear is either 28 spline or 31 spline not 30 spline (12 bolt chevy). If you have this style R/E (prob do with the 455), you will have 31 spline axles & if you want to upgrade, the search will be long for 3.42's.

Other possibility of R/E in your car...8.5 10 bolt Corporate rearend was also used in '76 big cars. There are actually 2 different versions of these used in a '76 big car. The better version has bolt in axles. The rear cover on these will be rouund & will only protrude from the rear of the axle 3 inchs. If you remove the cover, the 8.5 ring gear will have ten 3/4" headed lh thread bolts holding the ring gear to the carrier.

Ck what you have, & I can further advise you on how to get close to the ratio you need in a posi.

[ April 14, 2002: Message edited by: ol' Pinion head ]</p>