[locomotivebreath]

I’m wondering if my posi is worn out . I have a 10 bolt N unit in my GTO , it has the 4 pinion posi . I’ve only slightly stabbed the throttle since I’ve had this car back on the road but both wheels grabbed . I jacked it up last night to adjust the brakes and when I spun one tire , the other side rotated backwards ? I put it in 1st gear , both went turned forward . Could it just be weak ? I didn’t rebuild this rear during the resto because I wasn’t sure if I’d like the 3.90s ( which are awesome !) just put in new axle bearings & sealed it up . It was very clean inside . It hasn’t been used since the 70s . It came out of a wrecked GTO around 75 or so I just assumed it probably has less miles on it than my car . It doesn’t make any noise or anything . I remember years ago jacking up one side and trying to make it slip per the manual , I couldn’t and I was heck of stout in those days .

[Schurkey]

My "A-body" is the same. Posi is totally worn-out, no preload at all, but still works under load.

I bought new clutches, but I'm too lazy to install 'em. Maybe someday.

[steve25]

No need for posi additive fluid now till new clutch’s go in.

[locomotivebreath]

So it’s weak then ? My plan was if it was shot , then I’d order a Moser with 3.55s . This engine loves the 3.90’s though , u can feel it in its power band . Do I buy a moser or rebuild the N with the poor axle bearings ? I just cruise , I don’t hammer on it .

[AG]

Your 4 pinion posi is a cone type, not a clutch type that you can replace the clutches. You can get an Eaton clutch type posi for the 10 bolt, but they are expensive. If you have the money I'd get a brand new Moser or Strange 12-bolt with a Tru-Trac.

[lust4speed]

There is a difference between spinning wheels by hand and launching. The cone and clutch units have springs whose function is to give some lockup in zero traction conditions. Even when new this only amounts to about 260 pounds of force necessary to spin one wheel without the other, and this isn't very much (but difficult just twisting a tire by hand). You say that you can still do a two wheel burnout. Your unit doesn't have enough spring pressure to offer any resistance, but a good solid launch on asphalt will allow the spider gears to push against the cones and still deliver a burnout with both wheels. It's not dead yet but might not have much time left. A good rearend person can repair your unit and restore the pre-load and insure the cones won't be grounding out anytime soon.

[OCMDGTO]

Unless it's numbers matching if it spins both tires on a burnout I'd run it til it blew and then replace it with a 12 bolt/9"/Dana 60. When I was looking Strange had winter specials you might want to check out. Quick Performance is great for a 9". If you like the 3.90s why not get that on a replacement?

[locomotivebreath]

Thanks , I think I’ll just run it until it pukes then . If I can get a year or 2 out of it , I’ll have a more accurate opinion on my rear gear and my wife won’t be so wise ! This was a frame off debacle and she was pretty cool about the whole thing but I don’t want to bring up 3k on a Moser just yet .

[Schurkey]

Originally Posted by locomotivebreath

I just cruise , I don’t hammer on it .

I don't know why you'd even consider a new aftermarket "killer-strength" axle assembly, assuming that the gears and housing you have are in usable condition.

At most, an aftermarket differential in your existing axle housing. $700 instead of $3K, and a do-it-yourself job since you don't have to mess with the pinion gear.

Things might be different if your housing is bent, twisted, or cracked, or the ring 'n' pinion are shot because the original differential case explodes.

[ta man]

Originally Posted by Schurkey

I don't know why you'd even consider a new aftermarket "killer-strength" axle assembly, assuming that the gears and housing you have are in usable condition.

At most, an aftermarket differential in your existing axle housing. $700 instead of $3K, and a do-it-yourself job since you don't have to mess with the pinion gear.

Things might be different if your housing is bent, twisted, or cracked, or the ring 'n' pinion are shot because the original differential case explodes.

I agree..total replacement is the typical overkill on these forums. Aftermarket differential is the way to go.

[Scarebird]

I would talk to OPH (Roger) ans get a 8.5" with Tru-Trac setup from him.

[Verdoro 68]

Originally Posted by Schurkey

I don't know why you'd even consider a new aftermarket "killer-strength" axle assembly, assuming that the gears and housing you have are in usable condition.

At most, an aftermarket differential in your existing axle housing. $700 instead of $3K, and a do-it-yourself job since you don't have to mess with the pinion gear.

Things might be different if your housing is bent, twisted, or cracked, or the ring 'n' pinion are shot because the original differential case explodes.

Originally Posted by ta man

I agree..total replacement is the typical overkill on these forums. Aftermarket differential is the way to go.

I'm in a similar spot as the OP - my BOP 8.2 HD cone type rear is tired and fragile. When monzaz rebuilt it about 10 years ago he told me to go easy on it. With my new engine, I've been debating upgrading the rear. Would an aftermarket 8.2 carrier withstand 500 ft/lbs of torque with sticky tires at the track?

[Schurkey]

Originally Posted by Verdoro 68

I'm in a similar spot as the OP - my BOP 8.2 HD cone type rear is tired and fragile. When monzaz rebuilt it about 10 years ago he told me to go easy on it. With my new engine, I've been debating upgrading the rear. Would an aftermarket 8.2 carrier withstand 500 ft/lbs of torque with sticky tires at the track?

I'm guessing that with sticky tires, the pinion won't survive, never mind the carrier.

At minimum you'd want aftermarket axle shafts to go with the aftermarket carrier, but realistically I don't think this is a wise use of funds. The 8.2 is just not strong enough.

But I've been wrong before, and some of this depends on gearing and vehicle weight. A Firebird with 4.10s is different from a Full-Size with 2.73s.

[b-man]

Originally Posted by Verdoro 68

I'm in a similar spot as the OP - my BOP 8.2 HD cone type rear is tired and fragile. When monzaz rebuilt it about 10 years ago he told me to go easy on it. With my new engine, I've been debating upgrading the rear. Would an aftermarket 8.2 carrier withstand 500 ft/lbs of torque with sticky tires at the track?

Ask Santa for a new aftermarket 12-bolt built with the proper equipment to take some punishment.

Merry Christmas! 🎄

You have the engine and transmission to do the job, don’t forget the rear end.

[locomotivebreath]

I bought axles and the thicker bearing plates off of Monzaz when I sealed it up years ago . I’m too lazy to ever swap on slicks and the redlines are too expensive to fry . I searched for an 8.5 for a long time but had to give up in this area . The rear is the only part not original to the car so I was hesitant to spend the money on it .

['ol Pinion head]

Being a 4 pinion 8.2 PONTIAC STT carrier, & am assuming here that the carrier has never been sent out & rebuilt, I'd pull the carrier, mark the cast spacers left & right, remove the ring gear, clean the carrier with SimpleClean, not mineral spirits or other solvent that FedEx will raise questions about. Carefully box it in a well reinforced box, insure it for $400 & ship it up to Jim M. He will disassemble it & machine the back sides of the cones & properly shim them back up. On a 4 Piniin cone type carrier you can have this done once, then typ that's it. Years ago, I used to ship such well worn 4 pinion carriers cone type carriers to Calif & have them rebuilt. Jim is a lot closer to you & I believe offers this service.

[Verdoro 68]

Originally Posted by locomotivebreath

....and the redlines are too expensive to fry .

I hear that!

Originally Posted by b-man

Ask Santa for a new aftermarket 12-bolt built with the proper equipment to take some punishment.

Merry Christmas! 🎄

You have the engine and transmission to do the job, don’t forget the rear end.

It's around $3800 for a new Moser 12 bolt, but I could probably recoup some of that by selling my '69 XH posi. Maybe I can hunt for something local.

Right now I'm hesitant to run it too hard because it's slippery on street tires and the rear isn't strong enough for better traction. It sure would be nice to not feel like I have to baby it and to make a few passes at the track.

[b-man]

Buy the new 12-bolt and sell the 8.2 to someone who’s restoring a GTO.

Makes the most economic sense. If you play your cards right you’ll end up with a new 12-bolt for somewhere around $2k to 2.5k.

The cheaper local bargain rear end will likely be a disappointing waste of money, the new rear end built to your specs is a sure thing.

I wouldn’t invest another penny in that 8.2 rear.

[vicgto]

I have been meaning to post a similar question regarding my 8.2" 4 pinion rear end and if it makes sense to put any money into it but Locomotive breath beat me to it. A few years ago I machined the back sides of the cones & shimmed them back up as described by Ol pinion head in post 16. It has been working well for over 10 years. I have been considering putting in stronger axles and an aluminum cover with bearing cap supports but I'm not sure it's worth investing the money. I have read that these rear ends came with hot forged or cold extruded axles, does anyone know how to identify the hot forged from cold extruded axles?

[locomotivebreath]

The hot forged look really rough and have almost an apple core shape and the have a ring if you tap them with a wrench . The cast , look beefier and machined but are not , they will have a thud when u tap them . I have the cover that I bought off a guy super cheap , Yukon axles . I think I’m just a cruiser anymore so I’m undecided on what route to go . This was a frame off resto and just don’t have it in me to dump the clutch in it !