RAMBOW

Just thinking...

I'm building a new motor for my car, expecting around 425hp/550lbs of torque at the crank.

My car still has the stock 66 open carrier 10bolt 3.23 rear end.

What is the weak point with this rear? they've got the bolt in axles so its better than a 10 bolt chevy rear at least...

I'm Contemplating that a PowerTrax unit is cheaper than buying a chevy 12bolt and having it setup wth the gears i want... would that stand up to street abuse & occasional track punishment with drag radials?

Of course if the ring gears shatter and i have to get a 12 bolt, the powertrax wouldn't have been a good investment either...

thoughts?

507OLDS

If you are going to change everything it it anyway,meaning you are going to change the gears,& add some type of posi unit,then I would just invest the money in a 71-72 8.5" 10-bolt.Those are plenty strong,& cheaper than a 12-bolt Chevy.The ones from the Cutlass & Skylarks have the bolt-in axles as well.I don't know what gear you had in-mind,but your selection for the 8.5" 10-bolt is 3:08,3:23,3:42,3:73,3:90,4:10,etc.

Run to Rund

What Brian said! The 8.2 ten bolt is fine for a stock 6 cylinder on street tires. Put your money into something better. If you want to go "all the way" you will put about $2500 into whatever you pick, less for a partial strengthening. So, pick your starting point based on what you want it to look like, how strong you want, whether you have most of the stuff already for a rear. The good choices are basically 8.5 ten bolt, 12 bolt Chevy, 9" Type F (Ford), Strange Dana S60. The first will look the most correct vs. the 8.2 and comes with decent stuff (if the version with bolt in axles). The 12 bolt needs c clip eliminators and axles to protect your quarter panels. You can get the excellent Detroit Locker for the F and Dana.

gearheads78

I 3rd the 8.5 10bolt. Brian Trick above is a great source for parts too.

RAMBOW

Ok- that was basically what i was looking for- something to tell me not to waste money on the existing one.

I'll probably start looking for an 8.5 10bolt- seem to go cheap cause the chevy guys get pissed after they call on one to realize it isn't the chevy 12bolt. \

Not a big priority- getting the motor screwed together and into the car is the first.


thanks guys

507OLDS

The 8.5" 10-bolts that came in the 71-72 Skylarks have a cover that makes it look just like your existing 8.2",if you wanted the secret thing.This style also came in most of the 71-72 Cutlass/442's that were not built in Lansing.The other style of cover is round,with a lip that protrudes from 12:00 to 3:00.I have seen this style in all of the Lansing-built cars.I can supply something like this,all rebuilt,with your choice of gear,for $950.00 plus the freight,just to give you an idea.This would be a 71-72 housing & axle shafts,rebuilt GM clutch style posi unit,Motive Gears(any ratio),Timken bearings & seals,filled with fluid/additive,& ready to run.Backing plates included,but no brake hardware.Your existing hardware is the same.These rears are a direct bolt-in for your 66.However,you will need to shorten your driveshaft about 1" to accomadate for the longer pinion snout of the 8.5".If you are possibly changing transmissions,from a TH350,to a TH400,you could do all that at once,so you only change the shaft once.

Run to Rund

When it is time for the differential, keep Brian in mind if you want an 8.5. He has an excellent reputation on realoldspower. If I wanted the original appearance and good strength, I'd do just what he suggests.

monzaz

Well the 10 bolt 8.2 would probably hold as long as you actually rebuilt the rear and brought it back to specs again. As it is you sound like you want to just stick a power trax in and be done. WHICH you can do and it probably would work for a bit. BUt as you punish this 40 year rear all the slop will cause defection on the ring and pinion and carrier bearing areas. PLUS the stock 3.23 gears were cast in the 60's and the metallurgy mix was not as good then I have seem pinions literally 1/4 chunk themselves.
IF you re bearing the rear and power trax it it might do the job...But your spending 400+ on a power trax and then 100.00 on a re bearing your getting more than half way to a better rear.

The only other upgrade I would do is a better posi unit then the stock GM unit as it really is not supported well through GM anymore and will be harder to get parts for down the road. Spider gears are non existent these days from the factory and clutches are getting to the 200.00 mark also for rebuilds. PLUS the double LARGE window really is kind of with for big block power...I know I know GNs use them and people HAVE run good numbers with them...BUT if your going to do it... do it once. I am sure Brian has aftermarket posis too. Jim

507OLDS

Yes,an aftermarket posi unit is a good option,but from the info gathered from above,a well-tuned GM unit will work just fine.If you think you have ANY intentions of making more power,in the future,or wanting to go mid-11's or faster,then yes,you better opt for a different carrier,so you don't take any chances.Regardless,it's always best if you only have to do it once.

Warhead

If you were to race the 8.2 inch rear on slicks running low 12's- high 11's... the axles would twist (of course), then after about 3 sets of those, you would trash the pinion gears. Pontiac put some 4 spider posi's into their 8.2 inch 10 bolt Firebirds (they are about THE toughest units out there IMO), and that is next the logical upgrade-if you could find one. They will take more abuse, though.
Do the 8.5

Jim

507OLDS

Those 4-pinion posi units are a little stronger,but I've seen 2 of those broke in a 70 Cutlass that was running 12:90's at the time.He broke one at the track,put another one in,& I had to tow him home off the street.HOWEVER,these were NOT rebuilt or serviced posi carriers.They were unmolested,who-knows-how-many-miles units. One of those cheap guys that liked to do things over & over again,but he was getting a deal!! umm no.

wmachine

Actually, the 4-pinion cone carriers were used in the '67 W30s and also found their way into a lot of the 3.55-3.90 Anti-Spins in '67.
But yes, under severe use, tales of twisted axles are still the norm, and the aforementioned upgrades are still recommended.

f-85

You got that right. remember my 64 10 bolt from alittle over a year ago when i broke the pinion right at the seal.









BTW i still have my 64 carrier if you need it.

67442nut

Hey, Brian.
Is this the rear end you're talking about?
(Sorry for the hijack. Been wanting to verify this rear end.)
Ignore the posi unit. It's a POS Auburn.

DSCN3345.jpg
DSCN3343.jpg

monzaz

Yes that is the 10 bolt 8.5 rear 71 72 Buick and Olds.

Looks like a pretty big gear already in it. Jim

Sarum

Did you go with the PowerTrax unit and if so what is it like on the street? I am trying to decide what LSD to put in my '65 Cutlass
Also, is there any marking on the ring gear or pinion to tell what gear ration it is? Thanks

monzaz

Well if your going to replace everything anyway ANY 10 bolt rear will work fine usually... The gears being aftermarket will increase the strength factor there.
Both the 8.5 and the 8.2 use the same 28 spline axles so no big increase there unless the axles are replaced for better alloy parts.
Posi unit - this will be the weak area in most ALL rear ends. The more touch points you have the strong and more power the unit can handle.
IE 2 spider gear unit compared to 4 spider gear unit will increase the touch points to the side gears and increase torque delivery with out all the power being on a few points of the teeth... but more...
True trac worm gear will have as much surface area touch points as a 4 pinion spider gear posi also.
Power trax should be one of the strongest power delivery to the axles from the center section...but sacrifices quiet running as they click in turns... but are the closest step to the FULL spool with out having aXLE bind.
So the 8.5 does have a larger 1.625 pinion shaft compared to the 8.2 1.438 BUT again in aftermarket gears the rear end rarely fails on the pinion snapping off.
Spider gears and axle shafts are the highest % of failure in rear ends.

10 bolt 8.2 can only have 28 spline axles ...WE did do a 30 spline along time ago for Nostalgic racer but was expensive swap...
10 bolt 8.5 can be increased to 30 spline relatively easy with money.
10 bolt 8.5 you will also need to cut the driveshaft no matter what car you install it into ALWAYS... unless that car had a original 8.5 in it from the factory.

Last factor is the width...BY 1966 ...really most rears were 55.25 wide and only a low few if any were 54.25 very late 65 or very early 66 if a plant had left over rears. They all switched to the Pontiac WIDE track deal....

Really it all comes down to HOW MUCH torque and what your going to do with your torque for rear end size also MONEY...

Hope this info helps.

Jim
J D Race