[russosborne]

Happend upon the following and was reading it and read something confusing to me. Which isn't hard.

http://www.buickperformance.com/posi.htm

It is about finding/identifying posi units from later year cars such as trans ams, station wagons, etc.

What is confusing me is that the author, who I believe posts here also, mentions that to remove the posi unit from the donor rear end, you have to remove the c-clips that hold the axle in place. I thought that the 8.5 rear was like the 8.2 in that it didn't use c-clips?

Help.


Thanks,
Russ

[PONTIAC LARRY]

Most 8.5's use C-clips except some BOP ones in the early-mid 70's. IE: 71-72 Olds Cutlass Abody 8.5 are bolt in axle. All Chevrolet are C-Clip. Seen GMC Sprint 73 models with bolt in , 73-77 Olds , Pontiac, Buick 8.5 A -body are bolt in on the ones I have worked on. All F body and X body 8.5 are C-Clip as are 1/2 ton trucks

[russosborne]

Ok, so if I were to get a later posi like that in the link above, does that mean I have to use the c-clips also?
Thanks,
Russ

['ol Pinion head]

The 28 spline 8.5 posi carriers with #8 & #9 cast into the ends of them are for c-clip axles but can be used in bolt-in axle 8.5 rears & that's where most of the ones I reclaimed have ended up being used.

One thing George doesn't note in his article, is the claim rate for used S spring 8.5 posi's with good clutches. I started pulling these in the late 80's & have literally pulled & built rears with hundreds of these carriers. In the 8.5 posi carriers I've pulled in the last 15 years, a good 80% I've torn down needed all new clutches. Most of these posi's were out of low horse 70's & 80's big cars, not like they all came out of thrashed TransAms & Z28's. When I first started buying the GM clutch kits for these I paid little over $48 a box. Last ones I bought were over $122 a box. Several dealers were over $170 a box. Good luck finding any now, as GM discontinued them close to two years ago. I've heard Ratech was going to reproduce (read source) these posi clutches, but nothing from them so far. Without a source for new clutches, the used carriers are a gamble at best.

Another non serviceable part is the side gears, GM discontinued these over a decade ago & they were very expensive. I always robbed side gears out of the high ratio #9 carriers, then shimmed up the side gears with an assortment of side gear shims, some I had to have made.

[Scarebird]

OPH - what about this critter for my 71 Olds rear?

['ol Pinion head]

Scarebird,
I've installed a few True-Tracks in GM pickup housings in place of blown up Gov-locks, they seemed to work fine in that application. Have not set-up any True-Tracks in 8.5 A-body rears. If you want to try a True-Track, I believe there's a $30 rebate on them from Jegs, gets 'em down around $389.

[Cliff R]

I have yet to see an 8.5 with bolt in axles. All of the units I've aquired here, truck or car used "C" clips.

The really late units, after 1987 or 1988 will have 30 splines instead of 28.

Many of the later units also used Eaton locking carriers, which are governor controlled. This makes them more difficult to detect turning one axle to identify them as a "posi" type. It takes several hundred rpm differential in axle speed to engage the unit so they act like an open carrier.

One of my customers installed a True Trac in his 8.5 and completely destroyed it on his first outing to the track. It was a very early unit, but had been in service for quite a few years with street tires and no drag racing. He contacted the manufacturer and they provided him with a later unit, which is supposed to be a stronger/improved version. To date it survives fine behind a 455 making over 550ft lbs torque.

I've been using an 8.5 in the Ventura for decades. The original posi unit ("S" spring type) lasted fine until I installed my first and full race slicks. Blew the spider gears to bits on the first outing. Installed a second nearly mint condition used carrier, it blew up on it's first outing. Went to an Eaton posi with Mosier bolt in axles, and it lives fine now for 10 years and many hundreds of runs with good traction, 1.6 60' times.

It gets inspected every year right before Norwalk, and I replaced the axles last year as a maintenence item.

As good as the 8.5 has been to me since we got all the good parts installed, if I had to do it over again, I'd have bought an aftermarket 12 bolt or Dana 60 and been done with it......Cliff

[Overkillphil]

Quote by Cliff: "I have yet to see an 8.5 with bolt in axles. All of the units I've aquired here, truck or car used "C" clips."

X2! Russ, for all intents and purposes, you will be dealing with c-clip axles with an 8.5.

[SRR]

Just look at the axle flanges, if they have holes for access to the bolts then they are bolt in axles, if not then it's a "C" clip.

['ol Pinion head]

If you guys haven't seen a bolt-in axle 8.5 you haven't been paying attention.

Subject of the oem corporate S spring posis. Think all of us would would agree, the stock 28 spline S spring posi's have there limitations, that's one of the reasons I took exception to George's article. Why gamble with something that has strength limitations & one cannot get even maintenance parts for (clutches, clutch shims, new side gears)? Built with a 30 spline HD Eaton clutch posi & a pair of bolt-in Mosers, the 8.5 rear can be built extremely tough. Properly rebuilding an 8.5 S spring posi carrier, properly shimming the clutches up, & making do with it, then later needing to replace a shelled S spring posi carrier & often a damaged ring & pinion is where a lot of money can be spent. Cliff, I've seen your scenario several times.

To buy a Moser's musclepack bolt-in axle 30 spline 12 bolt rear with new 30 spline Eaton carrier, 1310 u-joint flange & have it shipped in one is looking at nearly $3300. yeah, you get new drums & loaded brakes.

Carefully buying parts, one can reuse their brake drums & brake backing plates & build two HD 8.5 A-body rears with Moser 30 spline tapered bearing bolt-in axles, quality gears, timken bearings, new HD Eaton carriers, and a 3R u-joint flange (bigger than Mosers musclepack spicer 1310) for same money. Can it have 33 splines in HD posi form? No, will it hold up, for many street-strip Pontiac's, it's probably overkill. I have a local V8 Buick street car friend whose car's been running a 30 spline 8.5 A-body HD Eaton posi rear for nearly 10 years. Low low 10's on the spray & high 10's on the motor. Mighty tough, all due to design, ie, a housing center section made by the factory with nodular iron, & if one actually studied it, has more pinion support in it than an oem GM 12 bolt. Oh the blasphemy! When built, he had a little over $1300 in it. In 10 years, I've replaced the clutches in the posi once. No need for a hernia inducing install of a aftermarket Dana 60 A-body rear in his car. He doesn't need it. I like Dana 60's too, but they're too d#mn heavy & then factor in parasitic loss. No thanks, only big Dana I need is under the back end of my Cummins Dodge.

Leaf spring rears: HD bolt-in axle 8.5 housing wise from the factory, there is nothing as drop in as there is with the 8.5 A-body rears. On '67-69 Firebirds, they are however, the same width as the '71-72 8.5 A-body rear. It is some work, but stripping off the A-body lower perchs & TIG welding on reinforced multileaf brackets in a jig yields a stock width 8.5 early Firebird housing or 2nd Gen F-body rear.. One can also cut the c-clip housing ends off the 1" narrower Nova 8.5 housing & jig weld on bolt-in axle ends (either new or used A-10 GM ends) then order bolt-in tapered bearing axles. I really like the A-10 bearing end 8.5 A-body housing, but they are tough to find & as housings and have always been used up quickly. About 15 years ago, I ran across a B series GM housing with A-10 housing ends. Out of local crusher yards & Pick-N-Pulls managed to cut off several dozen pairs of A-10 housing ends. After trimming them, putting a bevel on them in the lathe & properly welding them on, the A-10 ends look like they came on the leafspring 8.5 housings I've welded them on. Of course one can buy the CNC' ed aftermarket ends... I just like the stealth look of the A-10 ends a little better & a 2.9" OD A10 tapered bearing & seal is a whole lot less expensive than Mosers 3.150" road race tapered bearing. Both can support a very beefy axle & aggressive cornering. Last, if a car is built for great handling, it does not need sealed ball bearing axle bearings, something one needs to consider when custom ordering any performance rearend.

[Cliff R]

One of the kinda-stupid things I did after blowing up the second factory carrier in less than week, was to replace it with a 28 spline Eaton carrier. I saved a little money being able to re-use my bolt in axles, but after thinking it over, it would have been money better spent to upgrade at that time to the bigger axles.

In any case, my little adventure with the 8.5 was costly. It has held up quite well now for 10 years, and lots of dragstrip runs with good traction.

It shows no metal at all in the oil every summer when we do the inspection, and the posi-unit works fine, cross-pin still tight in the housing, etc.

We've been whacking it with over 550ft lbs torque with the last two engines, and it doesn't grumble at all. Now that I've said that, it's probably going to blow up on the next outing!.....Cliff

['ol Pinion head]

I remember you blowing up the 1st #8 carrier. I bet the Eaton has more life in it. Whats the best 60ft time with the Ventura?

Wish I'd have have bought fifty 30 spline Eaton 8.5 carriers when I could buy them at $280 each. Steel went up, then everything went waaaay up. I used to be able to count on GM small parts going up nearly 10% every March, then they started raising parts prices twice a year. I hate buying any parts from GM dealer, only buy what I have to from them today.

[russosborne]

Thanks for all the info, especially about the lack of replacement parts.
Sounds like I would be better off going with a Ford 9inch. I know a heck of a lot more about the Ford rearends anyway.
Of course, until I replace the stockish 350 that is in this it doesn't really matter. :-) Just would like to do it while I have the body off.
Russ

['ol Pinion head]

Skip the S spring oem posi carrier & won't have to worry about replacement parts.
New Eaton clutch type posi (no true-track), pair of Mosers, & gears set up in an 8.5 A-body housing & you're set.

price a aftermarket case 9" third member built right with good pinion support, quality gears, detroit locker, even in a cheap fabbed 9" A-body housing, will still need aftermarket upper arms & will prob have to adapt brakes. gets expensive if you want a strong rear. Built a few 9"s myself

[russosborne]

Thanks.

Already have the aftermarket upper adjustable arms. Wouldn't go with a locker, this is going to be mainly a street car. Lots more (from what I have seen) disk brake kits for the Fords. Still connected with Mustang people, so I could probably get a decent pumpkin. Would need to buy the housing already setup for the A body though.
One nice thing for me at least is being able to just pull the whole pumpkin out versus having to do everything/anything to the rear gears while it is in the housing.

But who knows at this point. Figure I will be doing good just to get this car on the road at all at this point. :-)

Russ

[Cliff R]

Whats the best 60ft time with the Ventura?

1.61-164 for most outings. Here's a copy of a couple of runs from a test and tune session earlier this year on our local 1/8th mile trackl.

I made them 23 minutes apart:

R/T: .505 .514
60': 1.6230 1.6289
ET: 7.3169 7.3188
MPH: 94.35 94.36

The car leaves smooth and clean, you can listen to the engine on this run. Not really smacking the tires all that hard with this new engine:

http://www.youtube.com/user/69tiger?...are_video_user

[Scarebird]

Originally Posted by 'ol Pinion head

Scarebird,
I've installed a few True-Tracks in GM pickup housings in place of blown up Gov-locks, they seemed to work fine in that application. Have not set-up any True-Tracks in 8.5 A-body rears. If you want to try a True-Track, I believe there's a $30 rebate on them from Jegs, gets 'em down around $389.

This will mainly be street - no slicks 225/70's. I really liked the SLP Zexel takeout I put in my 83 Camaro. Do newer 1/2 ton trucks with limited slip use these also?

[Skip Fix]

So OPH what do you do about aftermarket axles and factory TA discs not having a brake pilot long enough to locate the wheels? Machine down the axle brake pilot and make a longer "bushing" the factory OD to press on? MyMoser's barely stick out of the rotor.

Those 2.9 A10 bearings fit through the disc brckets?

[Pitch 400]

Yea, that's a good question. I asked Moser about using their bolt-in axles with the tapered bearings with the disc brakes and they said it would'nt work.

[mjm421]

Originally Posted by Cliff R

Whats the best 60ft time with the Ventura?

1.61-164 for most outings. Here's a copy of a couple of runs from a test and tune session earlier this year on our local 1/8th mile trackl.

I made them 23 minutes apart:

R/T: .505 .514
60': 1.6230 1.6289
ET: 7.3169 7.3188
MPH: 94.35 94.36

The car leaves smooth and clean, you can listen to the engine on this run. Not really smacking the tires all that hard with this new engine:

http://www.youtube.com/user/69tiger?...are_video_user

And Cliff gets the win!!!