Factory Buick Rear Differentials, What Were They Thinking?

I may have forgotten some of the facts here but this came up the other night and it got me wondering. In the years 65-70 Chevy had the strongest rears, the 12 bolt. BOP all had very high torque big blocks with weaker 10 bolts. What were they thinking?

 

I'll guess they were thinking the majority of new Buick buyers wouldn't be doing neutral slams, sidestepping the clutch at 5,000 rpm, power shifting, or putting on slicks and racing on weekends!
Street tire technology wasn't very advanced either.... lack of traction helped keep breakage down.

Or it might have something to do with the lack of availability of 12 bolt rears, or getting parts from another division....if those are even real issues.

The GS and Sportwagon rears did have upgrades such as larger wheel bearings and thicker axles, at least in the early years.

 

I've read the Buick 8.2 and 8.5 rears were extremely strong due to their design, its just the lack of available parts for the 8.2
Buick knew what they were doing, heavy car/big torque
The Chevy 12 bolt isn't all that.
C-clip axle retention
Axle needle bearings ride directly on axle shaft
The 10 and 12 bolt Chevy rears are embraced by the aftermarket, LOTS of parts available
Buick rears, ahh not so much

 

A Buick 8.2 is a VERY robust unit, bearings are huge , carrier stands are much more stable among other things. A 8.5 is just as good , you'd be hard pressed to find many 10bolt housing failures

 

My buick came from the factory with a 12 bolt. Oshawa!
And its a 350 car.

 

I see a lot of parts at the summit racing site for our 8.2 BOP's I have a 67 GS400. What parts are not available?

http://www.summitracing.com/search/...-end-components/axle-model/gm-8-2-in-bop-axle

 

Yours is a BOP 8.2 that ended with the 67 model. The 68-70 model 8.2 is different and Buick only. The BOP parts, including the gears, from the 8.2 BOP do not interchange with the 68-70 Buick only 8.2.

 

To each his own, I was not impressed with the 8.2 in my 69 Skylark because instead of having a bolt to secure the spider gear cross shaft, this one had a roll pin, and all the other good things about it didn't mean a thing after that roll pin sheared off and let the cross shaft walk out at 40 mph.

 

12 bolt Chev is Junk. I agree with Larry.

For 25yrs I had more calls on that rear end for parts than any other.

John

 

"Yours is a BOP 8.2 that ended with the 67 model. The 68-70 model 8.2 is different and Buick only. The BOP parts, including the gears, from the 8.2 BOP do not interchange with the 69-70 Buick only 8.2."
Thanks Flynnbuick.

 

The 10-bolt got its bad reputation from the 8.2" Chevy,and similar 8.2" BOP rears,but even the BOP 8.2" can handle more power than the 8.2" Chevy. The 10-bolt that Buick made is a very nice rear,and can take plenty of abuse. The 71-up 8.5" 10-bolt is just as strong or stronger than a 12-bolt Chevy. Yes,the 12-bolt Chevy was touted as the best,but there were stock 454 Chevelles & such that were breaking parts in those way back then.They were just good enough in stock form.They were never intended for today's power. One of the worst things they did with the 12-bolt Chevy was taper the axle shafts before the spline.That is where they all broke.You can compare any BOP shaft,or the 8.5" 10-bolt shaft,and the thinnest section is still considerably thicker than a 12-bolt Chevy shaft.And who was the genius that decided to have the axle shaft itself ride on the bearing rollers,and hold everything in with a c-clip.

 

The original rear end is still alive and well after about 10 years of abuse from a twin turbo 350:

 

I've had this conversation with so many people its nuts. When they look at my car (which still isn't what I'd consider a monster powerhouse) and I tell them it's a 10 bolt, they look at me like I have 3 eyeballs. Nevermind the Moser axles or anything else, so many just think "more bolts is more gooder!" I get told it'll never survive all the time. But it's usually the ever prevalent car show know it all who doesn't even have a car or the autozone employee that thinks he's the second coming of Henry Ford. I don't think they're indestructible by any means, but a properly built Buick 8.5 is at stronger than many realize.

 

Very true, I wish I knew back in the 80's what I've learned these past 10 years.
I had 3 BOP 10 bolts on the garage floor, one was the original 3.08 peg leg outta my GS, but I got a 12 bolt Chevy PAAHZI rear for free, I had another 12 bolt Chevy open with 3.42 gears, I threw that away along with the BOP 10 bolts, how freakin' stupid I was
I kept the PAAAHZI 12 bolt so I'd be cool, ahhh, like they say, hind sight is 20/20, whatever that means:bglasses:

 

I run the 8.5 corporate in my GS. Went with the 30 spline Eaton carrier and Moser axles as well. I think the 12 bolt is a good strong rear. I just prefer the bolt in axles and its the rear my car came with.

 

So I decided to delve into the rear end quagmire and learned allot that I thought I'd share with the group. Many of you probably already know most of this but this is for those that don't.
There is a 8.2" 10 bolt Early BOP 64-67, an 68-70 8.2" 10 bolt Buick only and then the 71-up 8.5" 10 bolt corporate.
The early BOP's aren't even exactly the same even thought they share many features. Here are two links to sites where I learned this and more. I hope it helps.

http://www.jdrace.com/diff_id/10bBOP_Early.htm Also has a blog that is informative
http://www.differentials.com/gm-8-2-bop-differential-parts

BOP 8.2" info from an Poncho blog
All factory 64 & 65 Pontiac 8.2 Safe-T-Track & Olds 8.2 Anti-spin units were 2 pinion units. All '64-65-66 model production 8.2 Pontiac housings were gray iron... very susceptible to pinion deflection under high torque loads. Pinion deflection is big reason why all gray iron GM 8.2 rearends blow up when exposed to heavy torque loads, no matter what posi carrier (rebuilt 4 pinion, eaton, auburn) & good aftermarket axles are installed in it. The weakest gray iron housings ever cast were used in '64-66 Olds & Buick 8.2 rears, they are junk.

4 pinion cone type 8.2 Pontiac Safe-T-Track carriers were introduced for '66 models with the low ratio 3.36-4.33 gearsets. They were also used by Oldsmobile in '66. Pontiac dealers were advised to replace destroyed '64 & 65 two pinion Safe-T-Track units with the 8.2 HD 4 pinion Safe-T-Track carriers.

If one has a Pontiac 8.2 2.56 or 2.78 Safe-T-Track rearend, it is a 2 pinion, as no 4 pinion units were made for the high ratio (2.56 & 2.78 rears).

Mid ratio 4 pinion Safe-T-Track units were produced in early (through '69) & '70-72 8.2 Pontiac styles. The mid ratio 8.2 Pontiac carrier was used with 2.93, 3.08, & 3.23 8.2 Pontiac gearsets. While there were many 4 pinion Safe-T-TRACK rears built with gray iron housings, there never was a 8.2 HD SAFE-T-TRACK rear built with the mid ratio gears & 4 pinion carrier.

To qualify as HD SAFE-T-TRACK, the 8.2 Pontiac rear was built with the nodular housing and the 4 pinion carrier AND the special forged axles. Tons of '67-72 Pontiac 3.55 SAFE-T-TRACK rears were built with nodular housings, but with the the standard duty '67-69 or '70-72 Pontiac 8.2 axles.

Buick built their own HD 8.2 BUICK 10 bolt rear from '68-70. It takes it's own gearsets (like their 2.93's, 3.08's, 3.42's & 3.64's) & its own different series 4 pinion posi carriers. These Buick 4 pinion 8.2 posi carriers had different spline side gears & their own stagger for different ratios. If one is not careful buying used parts they can end up with a 4 pinion Buick posi carrier for intended Pontiac 8.2 usage.. The '68-70 Buick 8.2 posi unit & single track carrier takes a 12 bolt carrier bearing on the drivers side & normal 10 bolt carrier bearing on the passenger side

It's really not a mess, its actually easy to understand, if you look at it as a continuation of improvements as power levels rose as the torque loads increased with more powerful engines. Through the 60's GM had 4 divisions building A-bodys in the US, & each division basically had its own gear & axle assembly at least enough autonomy that in '68, 69, & 70 each division had its own rears. GM, Ford, Chysler all increased the strength of their rearends in their highest performance vehicles as the decade rolled on. Warranty claims is not what they wanted, so they upgraded... at least behind their performance engines.

In GM's case, the common Chevy 12 bolt was not the General's strongest factory A-body or F-body rear. Not unless you happened to to have been one of the very few who ordered a COPO Chevelle, an L78 or LS6 Chevelle, or COPO Camaro, or an over the GM counter version of one the truly HD 12 bolts for those cars. The rest of Chevrolet Divisions Chevy 12 bolt offerings, the vast majority of Chevy 12 bolts built had weak axles coupled with their really weak link: the brittle spider gear/side gear combination. Truth be known, the 30 spline standard duty Chevelle 12 bolt axles lack a lot in strength to the best bolt-in 10 bolt axles, thus counting axle splines really won't tell the whole story. In the case of factory Pontiac 8.2 axles, it wont tell if a 28 spline sealed bearing axle is a regular light standard axle or if is is one out of HD SAFE-T-TRACK rear. As far as metallurgy of the 12 bolt Chevy center housings I have not studied that a ton. Would love to compare a 69 BE coded Camaro 12 bolt to the '69 BV I have in my racks. Both are 4.10 positraction Camaro units, the BE has all the good stuff & has a different casting number on the hsg. Nodular iron, a good bet.

More on axles... the bolt in axles out of '64 or 65 Olds Cutlass or 442 or Buick Skylark or '65 GS will bolt right in a '64 or '65 Pontiac 8.2 rear, and are the same strength std duty axle. Now what about the fellow who just bought a early GTO or LeMans project car & over the previous years, the Pontiac's original rear was swapped with the weak early Buick 8.2 out a '64-66 Cutlass or '64-66 Buick Skylark. They look nearly identical, but the strength of the gray iron center section early Buick 8.2 is not near as strong as the "weak" gray iron Pontiac 8.2 housing out a '65 Tempest, LeMans or GTO. Olds even specified the Pontiac 8.2 in many of its higher torque application '66 442's. that housing was just Pontiac's standard '66 gray iron 8.2 housing rear. Not the nodular 8.2 Pontiac housings which first started showing up in '67 Pontiac A-body 3.55 Safe-T-Track applications. The nodular hsg 8.2 was really needed behind really strong applications like the '66 L79 W30 442. Olds instead dropped the 8.2 & developed the type "O" 10 bolt rear which lasted a few years.



Buick 8.2"
The 8.2 Buick is FAR SUPERIOR to many of its rivals in so many ways including:
•Buick 8.2 uses 10 7/16” ring gear bolts (same as Ford 9”)
•Buick 8.2 uses larger 27 spline pinion yoke as opposed to 25 spline Chevy 8.2
•Buick 8.2 uses a massive 1.875 pinion bearing for rigidity that dwarfs the Ford 9”(same as Dana 60)
•Buick 8.2 uses an oversize bearing and cap on the ring gear side of posi unit for strength
•Buick 8.2 uses the Mechanics 3R U-joint for reliability
•Buick 8.2 uses a much lower pinion center line (hypoid) in relationship to the ring gear providing much more tooth
•contact area as does the Ford 9”
•Buick 8.2 uses axles retained WITHOUT using the dreadful “C” clip. All Chevy 10 and 12 bolt rear end use this “C”
•clip system and many quarter panels have been destroyed from this poor design.

 

Thanks for sharing all that :beer

 

Craig, maybe I missed something, but you seem to have skipped over the 67 Buick 8.2 ? You went into great detail explaining the differences in 64-66, and 68-70, and their applications, Nodular vs. Grey iron, but what about the 67 unit specifically?

 

There is your facts...
C-clip axles were CHEAP.... reason chevys got them... Pontiac rears had the 4 pinion posi units ...which were stronger than the stock 12 bolt chevy factory posi unuits. The 12 bolt chevy had TOO small of pinion spider gears whch actually blew up quite frequently. (now all the aftermarket companies have harden forge spider gears solving this problem. ALLOY axles mad ethe c-clip axles much more reliable to breakage also.

Really back in the day the Pontiac rear was the strongest... Bearing caps were extremely stout posi unit was the best with 4 spider gears and 2 side gears, bolt in axles...Bearing caps for the Pontiac were even thicker than the 8.5... it was better.
NEXT came the 12 bolt olds W30 rear...it had a 8.5 ring and a larger inner pinion bearing for better oiling... But still had the 27 spline pinion yoke shared with th e Pontiac 8.2 rear. Buicks Pinion yoke was way weaker than the Pontiac and 12 botl olds. Posi unit spiders were better designed in the NEW 12 bolt olds (only 2 pinion gears and 2 side gears) BUT this rear had 31 spline BOLT IN AXLES.... Larger carrier bearings too in the W30 optional rear. Regular 12 bolt olds had the same 28 spline and smaller 10 botl carrier bearings

67 68 years only had the w30 optional rear end with 31 spline axles and large carrier bearings.... then was degraded to 28 spline bolt in axles in 69 70 (NO 31 spline optional axles in these years).
Then came the 10 bolt 8.5 corp rear which is what became the standard for GM cars and 1/2 ton trucks. still being used till this day... it was upgraded to 30 spline in 1990-1999... which was NOT too bright by GM because they forgot to increase the carrier outer bearing hub diameter...causing failure under heavy towing and loaded trucks.... the bearing hubs would sheer off causing massive rear end failure.
This was again corrected after freakin 10 years to the 8.625 rear where larger 12 bolt carrier bearings were used and that is where we stand. Now they are even changing the pinion inner and outer pinion bearings...BUT the 10 bolt 8.5 gears are all the same from 1970-2015.......... Last time a car had the 8.5 rear was 1996.

Jim Mitschke
J D