i have a 1971 GS stage 1 car. the drive shaft came out of the car (see earler post) and it damaged the pinion yoke of the car. i bought a 8.5" pinion yoke from someone on this board (THANKS!) but unfortunately it was not the one that would fit the car (it was much too large). i called the original owner--who is a buick restorer in the NE, and he told me that the rear end in this 1971 car (which he bought new) was a 8.25" rear end with a cone posi unit inside, not the 8.2 or 8.5. he said that it was only used in one other car, 1970 RA pontiac cars, and that parts were not made for this rear anymore. he said that these rears were placed in these cars from late 1970-very early 1971. it was because the 8.2 rears were not handling the power from the stage 1 cars. is this true and does anyone else know what this rear end is. i have tried to get the ID numbers off of it but i cannot find them. thanks john
8.25 Well... I think the bop 8.2 1970-1972 (mostly pontiac) are really 8.25. The chevy 8.2 is I think actually 8.125 ring gear diameter. Just nick names that are easier to say and I D. In 1970 the BOP had 7/16" reverse thread bolts and may have increased the the diameter of the ring gear a bit, but kept the ring gear bolt pattern the same. YOU can mount a 8.5 ring gear to a 8.2 carrier with 7/16" bolts. The yoke was also up graded using the 12 bolt 'olds' 27 spline yoke which are beefier than the old style 27 spline 8.2 BOP yoke. So if you can find one of those 'o' type yokes you can use it with a 12 bolt 'o' seal in your 8.2 BOP 8.2(5). The cross pins on the 1970 -1972 Pontiac and 1970 olds were increased in diameter too. 1968-1970 12 bolt olds was also actual like a 8.5 carrier in them. Well I hope someone else can help shed somemore light that is all I have to offer on it. If there is wrong info lets hash it out so we can get this man some good info. Jim
thanks monzaz! that helps. so i have a cone posi 8.2(5) rear end in my 1971 stage 1 car. this 8.25 rear is what everyone calls the 8.2 rear, is that correct? so does anyone make pinion yokes for this car? john.
John, am not sure about the story. The HD Safe-T-Track 8.2 Pontiac rears used in '70 RamAir GTO's with 3.55-390-4.33 gearing will use a nodular iron hsg (has a large cast N on the nose of the hsg & will use HD forged axles with tapered axle bearings... external seals. These also came with 4 pinion Safe-Track carriers, though the presence of a 4 pinion Pontiac Safe-T-Track carrier alone does not make a HD Safe-T-Track 10 bolt. The Nodular Pontiac 8.2 housings do not use a typical Alpha-numeric date code in the webbing. Instead from '67-71, they are ID'ed by casting number & julian date code. In building 8.5 A-body rears I've identified '71 8.5 A-body housings cast as early as Feb of '70. These very early cast hsgs were pulled from Olds & Buick A-bodys built in Aug of '70. As far as the presence of a cone type posi unit, the '71 model factory posi 8.5 rears often used Warner-Motive cone type posi units. This style posi eventually wears out. Over the years, I've pulled quite a few out of original '71 GS-442-TransAm- Formula-Z28 8.5 original posi rears. All were replaced with either reman corporate "S" spring, or new Eaton carriers. Your pinion yoke problem would not be related whether the 8.5 rear originally used a Warner-Motive cone type posi, an early Eaton 8.5 posi, or a corporate "S" spring posi. There are basically three different 8.5 pinion yokes & all will fit on any 8.5 pinion. -Spicer 1310 version used mainly in chevy 8.5 applications up through '74, -the common 3R version used in all '71-72 8.5 A-body -flat round style flange like used on '76-79 Sevilles & many light duty '71+ B series. To help differentiate, all 8.5 pinion yokes will the fit 30 spline 8.5 pinions. Pontiac 8.2 10 bolt pinions used the 27 spline yoke, while '65-72 Chevy 8.2 (c-clip axle 8.2's) mated to a 25 spline pinion. Hope this helps. Got Posi? :3gears: Roger
Several thoughts I have with the original owner story revolve around the difference in driveshaft length. Factory use of any 8.2 style rearend in a '71 model Buick GS would require the use of a longer driveshaft... same as used in same transmission style '70 GS. Not something an assembly line worker would have ready access to when originally assembling such a '71 model Buick A-body. Considering the Fall of '70 UAW strike lasted from aprox Sept 12th through Nov 15th, some partially assembled cars "stuck on the line" were completed by management. Dave H can confirm this. Even such odd assembly methods would not explain why '70 length driveshafts would still be in asm line bins well after a plant had been building with the '71 model specific length driveshafts. Typically, non conforming parts from previous model year were sent to GM Service Parts. IF factory documentation exists, say notations in a '71 BUICK assembly manual, a 3.90 ratio 8.2 Pontiac HD-Safe-Track rear could be a possibility. Got Posi? :3gears: Roger
wow..... ok here is some more information. the car was ordered from Erkanin buick in stowe MA by the parts manger. it was ordered to drag race. it was built in Framingham MA. it is a date-on-block confirmed stage 1 car. it was a stripper buick (no ac, power windows, etc). it was ordered origianlly with 3.90:1 gears for racing. it now has 3.73:1 gears. i was told that this rear was placed in the car by buick because it was a stronger rear for racing purposes. the only numbers i can find on the rear are on the webbing near the center housing. i will check tonight for the N in the casting. the car is at the shop so when it goes up on the lift, i will scower it for numbers. does this provide any further info? john
8.2 Buicks 68-70 did not have 3.73 ratio . They had 3.64. Since it has a 3.73 it would likely be a 8.5 inch GM corporate as would be expected for all 1971 non Canadian cars.
i would have thought that it was a 8.5 also but the 8.5" pinion yoke did not fit the rear end. and the one that was on there was noticably smaller than the 8.5 pinion yoke. so the original owner told me that the rear was a 8.25 (which i had not heard of until this post). so here is my delema. also i have to count the rotations of the tire to get a better idea. it is possible that it is a 3.64. i do not know for sure, i am only going by what i have been told regarding this car. john
To Be or Not to Be? 8.2 or 8.5 John, I would've imagined when I sold you the parts needed to get your rear up to snuff that your 71 had a 8.5 10 bolt in it. The 8.5 diff will have squared off blocks on the lower corners of the diff carrier housing. The 8.2 does not. You can find pictures by doing a search in the rear end section to see what I'm talking about. If you do end up having the 8.2 I will purchase the parts I sold you back. Just let me know. :TU:
Something very odd here. 3.90 HD Safe-T-Track 8.2 (Pontiac rear) was avail in '71 Pontiac 400 4bbl equipped GTO's & GT-37's. It is very seldom ordered, as the 3.55 ratio worked very well for most, & one had to order the performance axle ratio, when one ordered an M22 trans with the 400 4bbl to get this ratio of rear. It also required HD cooling (4 core rad). I ran the GT-37 survey for many years & only encountered two such '71 M22 3.90 equipped Pontiac a-bodys, one in a very early red Fremont built GT-37, the other was in GTO. Framingham also built Pontiac A-bodys, though very few. Would love to hear more on this r/e, when you get achance to examine. End up needing an 8.2 yoke, I should have one. Got Posi? :3gears: Roger
i agree. this is very interesting. i was unaware that these rear ends were swapped like this. but the original owner swears that this is the case and that this was not something that cobbled together. and i know for a fact that this is not a 8.5" rear, and he told me that it was originally ordered with the 3.90 gears. the car has some facinating history and i have pics of it in the 1970's and 1980's drag racing in SA classes. when i get the car back i will go over the rear with a fine tooth comb and give you guys all the info. thanks john
ok i have one more question for oPh and speed70 (and anyone else with some info). is this pontiac HD rear end with the cone posi going to have the same pinion yoke as these 68-70 8.2 inch rear ends? i am still wait for my $150.00 pinion yoke o No: john
ok here is the skinny. the flange that was on the car was not the right flange. it was a smaller flange that fit the pinion gear but that used a larger gasket to keep it from leaking. now i have the right pinion yoke. i should get teh car by the weekend so i can look for those ID numbers. john
