How much torque will depend on how the vehicle is torque loaded. With slicks on a car that can that truly hook, I'd hazard 350-400 ft lbs. Buick engineers didn't think very highly of the Buick single rib gray iron 8.2's, thus they did away with it, same time hp & torque levels were rising. I personally won't build on gray iron Buick or Pontiac 8.2 for anything other than stock putt-a-round cruisers, the housings are weak & I've picked p the pieces of too many 8.2's that have blown up behind much higher than designed torque levels. Here's a rundown, a progression of GM rearend designs used in GM A-bodys from 1964 up through '72. Each GM division had a lot of atonomy to build their own designs, at least up til 1970. The modern corporate 8.5 evolved at this time. -------------------------------------------------------------------------------------------------------------------------------------------------------- Let's do a run down of GM A-body rears. -8.2 Chevy 10 bolts are weak. Easily the #1 ten bolt to give 10 bolts a bad name. The 8.2 Chevy rears lack pinion support, plus have c-clip axles. Check what Chevy used them under... cars with under 295 hp & little torque. -Also really weak are the '64-67 Buick cast (single rib) 8.2's. Lot of pinion deflection. Olds A-bodys in '64 & 65 also used this style housing. By '66, the highest hp & torque '66 Olds A-bodys did not use these, instead, they used the next (stronger) 10 bolt... the gray iron Pontiac 8.2. -Next slightly stronger is the gray iron Pontiac cast 8.2. These had converging ribs on each side of the housing in an effort to limit pinion deflection under ever increasing torque loads. The common as dirt gray iron 8.2 Pontiac housing is what the avg Pontiac owner thinks he can throw $900-1000 worth of new posi, gears, & bearings at, along with sticky tires & 450-550 ft lbs of torque... & it will last... lol. Might last a while, at least till one gets the car to hook. Pontiac engineers figured this out & resorted to casting its heaviast duty 8.2 center housings out of nodular iron. Long ago, I quit building the gray iron 8.2 Pontiacs for street/strip cars. -Next stronger in the "food chain" are the '68-70 BUICK 8.2 10 bolts & the '67-70 Type "O" Olds 10 bolts (12 bolt smooth cover). Problem today with either of these rears, & esp with the '68-70 BUICK 8.2... near impossible to find half way affordable good low ratio gears & posi's. Even built up, both still lack the pinion support of later 8.5's & 12 bolts. -Next stronger in the GM lineage, the stock 12 bolt Chevelle posi rear. Once the 295 hp rating was met, Chevrolets received a 12 bolt. Way overated in the common low performance versions. Most 12 bolts came stock with weak light duty axles, & all 2 series & most 3 series oem posi carriers came with brittle 10-18 side-spider gear combo's. Basically makes upgrading these problem spots a must. -Strongest 8.2 10 bolts ever built are the '67-71 Pontiac HD Safe-T-Tracks. The HD Safe-T-Tracks nodular iron center hsg decreased movement of the pinion under heavy torque loads. HD "hot forged" axles were also used. Even the HD Safe-T-Tracks have their limits in strong street/strip A-bodys. -McKinnion cast BOP useage 12 bolts are the next stronger, had stronger axles & 3R u-joint flange. Down side... most had 10-18 combo side gear combo & axles were still retained by c-clips... not good. -Stock '72 8.5 A-body posi rear is next strongest. I would include the '71 stock posi 8.5's but every one I've disassembled had a Warner-Motive cone type posi unit. Similiar to a std duty Auburn posi, the Warber Motives eventually lose their posi capability. Big postives for the 8.5, is more pinion support AND bolt-in tapered bearing axles. When combined with the '72 & later stock "S' spring posi's, which had larger spider gears are a huge plus. Wide range of aftermarket parts make the 8.5 even more versatile. -Strongest GM A-body rear built by GM were special 12 bolts used in '69 COPO Chevelles. Try & find one, LOL. Still used c-clip axles though -------------------------------------------------------------------------------------------------------------------------------------------------------- Got Posi? :3gears: Roger
Wow, thanks for all the info. Is there a more modern transplant that is strong and durable that could do the job such as a later year? If this question shows that I am ignorant- it's mostly because I am.ou:
jbird76, No question is too ignorant, some just take a lot of writing to get the point across. I put the above list together about a year ago, to show the progression of different strengths of GM A-body rears. Probably should have written it better, but the jist is, as each GM division developed stronger & stronger engines, each divsion had to upgrade its rearends as well, as each division had to deal with warranty issues. Rearends like the gray iron 8.2's just wouldn't cut it esp when higher torque engines were installed then. Ever since that time, with wider stickier tires & higher torque engine builds many of the 8.2's came up short. For the last 15 years, when confronted with delimma of blowing $$$$ on rebuilding an early 8.2 with new lower ratio gears & an Auburn carrier vs building a rear which from its original design, was so much stronger, myself & many other builders have gone with building the stronger design. Usually, that stronger design has been the tapered bearing axle 8.5 A-body rear, it is the superior choice & a very versatile r/e to build, lots of factory & aftermarket parts support. Want a bargain rear for a 13-14 sec cruiser type A-body, no problem. Want something that can easily be built to hold up to sub 1.50 sec 60 foot times at the track, no problem. Still, in some cases, a customer believes he needs what will turn out to be much more expensive upgraded 12bolt. To be delivered next week, have an upgraded '65 12 bolt Chevelle rear going out. Its one of the last narrow 12 bolt Chevelle housings in my racks. Cores for these are expensive, I've always paid a premium for them. The '65 Chevelle 12 bolt sold as built up with an upgraded Eaton posi carrier, new 3.42 gears & axles, it's an easy $1500 ticket. Still has c-clip axles, though. For $600 less, I could have built a same ratio very similiar strength 8.5 A-body rear that would have fit the same car, be it 9/16 of an inch wider on each side. Customer suffers from "Gotta, Gotta have a 12 bolt" thought process, so he's paying the extra for the upgraded 12 bolt. If same car was mine, no question, it would have recieved a blueprinted 8.5 A-body posi rear, I've paid to have installed my last nos quarter panel on a car due to a broken c-clip axle. In one of my own factory 12 bolt installed Pontiacs, the original 3.55 HD 12 bolt is now setting in the rack, replaced by a HD 30 spline tapered bearing axle 8.5 A-body rear. Later this Spring am building another one for my other 455HO T-37. Hope this helps, hope I didn't get too wordy. Got Posi? :3gears: Roger
AMEN OPH!! The toughest part of "selling" someone on the BETTER part for their application is the fact there are many variances in O.E. design, new technology VS. old etc..etc. Unfortunatly as a rebuilder you have to be descriptive and spell it out and that becomes time consuming but worth it to the customer/consumer in the long run.:TU:
