47 Convertible

Rear end in picture is in my 47 Olds convertible. It was there when I bought it as a 'project car'. I've been told it is a "60-something GTO" but have no real idea if this is so.

Identifying marks: Scalloped rear cover, 10 bolts hold cover on. Stamped 'WF' on left, rear side axle tube. Cast in numbers on back of 3rd member housing: 9783393 on lower left of back of housing and 'N' on upper left of housing.

It feels like there are two ribs on ea. side of housing but the top one is smaller and shorter so I'm not sure. Wish I knew more about this.

Also, I was told this was an 'open type' as opposed to a posi. Ratio appears to be 3.23:1 by turning the wheels and watching the U-joint turn. Wheels turn in opposite direction.

Any positive ID appreciated as I would like to change this over to a posi rear end and need to know which type is the right set up for this. Thanks very much for any help.
Jerry

Bluevista

I searched old posts over at the Performance Years GTO forum and
here's what they say.

" For '66, the 10 bolt center casting was p/n 9783393.

For '67, the 10 bolt center casting was p/n 9783393 (no change). This casting was also used for the '67 Firebird rear end assembly, even though the axle tubes were different and the upper ears were not needed/used.

These earlier application castings seem to show up in rear end assemblies for other GM Divs., especially Olds. Not sure if they just used Pontiac's casting and assembled their own Axle Tube & Diff Housing Assembly or if Pontiac produced the rear ends for them, identical to the Pontiac units."

I do know that WF is a 3.23 ratio open rear, otherwise I know nothing.

47 Convertible

Thanks for your efforts. My rear end does not have those upper ears on it so it is possible it is from a Firebird or whatever else had the same no.s but no ears. Your info on the WF code coincides with what I was told by someone else so it seems good. Would have been too much to expect a posi.

Oldsguy

See if you can contact our member 'Monzaz' he does a lot of rear end work.

507OLDS

That's an 8.2" BOP rear.

Run to Rund

The 8.2 rear isn't very strong but 507Olds has a lot of experience beefing up GM rears on a budget, or all out.

507OLDS

You can get aftermarket axle shafts for that rear,and there are posi units available.They did a lot of work to fab that thing in there,so it would be nice to keep that in there,as long as it is done correctly.I would put an Eaton posi unit in it,if/when you decide to go through the rear.The shafts could come later,as you can change those without disrupting the center.Just unbolt them from the ends & slide them out.
What are you plans or expectations with the car?

47 Convertible

The plan is a resto-rod 47 Olds Convertible repowered by a '68 455 which has been rebuilt and warmed up a little to 461, high comp. pistons at about 9.5:1, comp cams 268XE along with new valve train, intake ports matched to Performer manifold, engine balanced, shorty headers, HEI, Ruggles rebuilt Q-jet of 68 vintage. Rebuilt and strengthened 700R4 with heavy duty TC and what I now know is the 8.2 BOP rear. I intend to have all the rest of the drivetrain components fully able to take the 461 torque. Don't wish to be left high and dry by rear end, driveshaft or transmission issues.

It is to be driven on the street, no drag racing in that heavy convertible body and frame. But I expect it will get the occasional light-to-light race or burn-out and I don't want to be embarrassed by a rear end or axles that go out in the middle of a little bit of showing off.

I have a decent GMC pickup that is my day-to-day driver and a 36 Chevy street rod that is a real show off car. It got a lot more spent on it than the Olds will. All of which is to say the Olds isn't going to get many miles on it unless it proves to be a better road trip car than the 36.

I want to thank you for taking the time to give me more information on the rear end. If you wouldn't mind answering a few more questions I'd appreciate it.
1. What is the weak link on these rear ends? Sounds from your comments like it might be the axles. If the R&P or the bearings aren't the weak link I'd like to keep the 3.23 gears as I think they will be about right with the OD trans and 16" wheels and wide whites I want to run for tires.
2. Seems like Eaton is about the costliest positrac setup. What are the good points of Eaton vs. the other brands. i.e., why would you prefer Eaton and not the others?
3. Does the 8.2 rear require the spring/disc pak type posi?
4. Given the U joint yoke on the rear end will I have any problem getting a driveline built in terms of a common and readily available U-joint at the rear?

You are correct that the previous owner spent some time and effort to get that rear end in there. As you can see he kept part of the original Olds rear suspension and managed to hook it up with the newer rear end. The car also has a Groundhawg built MII front suspension with 11 in. Granada type rotors, GM single piston calipers and 2" lowering spindles. Steering is Thunderbird R&P at 3 turns lock to lock. At the time I got it he had a SBC and older 700R4 in it but they were core quality and never intended to run. I couldn't bring myself to keep a Chevy in an Olds.
Jerry

Rickman48

The weak link are the rear carrier caps - if you put some sticky tires on it!
They make a cast rear cover with lock-bolts that hit the cap at the middle that help, too!
I believe Strange makes another thicker cap - but requires machining, and I remember someone having 'straps' - over the caps.

Eaton has the spring/disc pak - reason for cost, but aso rebuildable.

U-joints are available at any Auto Parts store.

Sounds like a fun one - pics would be nice!

47 Convertible

Thanks for the information. I've never dug into a rear end and made modifications and all the business of setting one up correctly with proper tooth engagement, shims etc. is a little daunting. So I doubly appreciate good advice. It sounds like I can stick with the 8.2 BOP and with some modifications can get reasonable service as long as I don't continually flog it.

The guy who built the 700 transmission knew what the engine was and built accordingly. I'd like to have the strength added to the rear end before I get the car on the road. I'm probably looking two years down the road with budget and time constraints.

Who provides the carrier strengthening stuff?

I don't plan to put really wide sticky tires on it. Probably 16" with 7" wide wheels and 7.5-8" wide tires, 27" tall. I plan to to run radial street type tires.

I would imagine that prices are all over the map depending on what one chooses and what is available. Do you have an idea of the cost range for the strengthening needed? I'd like to do a good job without breaking the bank.

Again, thanks to you and all others who have been generous with information and advice.
Jerry

507OLDS

He is referring to an aluminum gridle cover.It puts preload on the caps to help prevent deflection.Companies like LPW,Strange,Moser,etc. have those.Your ring & pinion will be fine.The pinion is already set,as far as depth goes.When you change carriers,you will need to check or reset the backlash to the current setting.The Eatons have the clutches & are rebuildable.

Run to Rund

Where are you located? You can spend money to upgrade the 8.2 but if you ever get real traction, it could break spiders, axles, etc., whatever is still near stock. I have also heard of the housing splitting. Another possibility woulld be to have a shop such as Quick Performance in Iowa build a bolt in Ford 9" which you could upgrade for similar money to what you would put into the 8.2 if you tried to upgrade it. The only advantage to the 8.2 is that you already have it. A full upgrade would include welding the axle tubes to the center (tricky to do right), axles, caps, best posi that can be made to fit with machining (like the 8.8" Ford), billet companion flange. The 9" Ford would be a lot stronger in the end for similar or a bit more money. you could get two nodular or aluminum centers with different gear ratios, making swapping ratios easier.

Yes you could end up with $2-3K in the diff. However, what is the car worth if you crash it because the rear blew up? Usually that doesn't happen, but give it some consideration. If you had the 12-bolt Chevy or 8.5" GM, you would be better off as a starting point. 507Olds and others build up those rears for a lot of power. The 8.2 could be built but would still be weaker, and the money wouldn't buy near as much strength as if you started with a better platform.

Olds bought HD 3 speed manual trannies from Ford so I consider Ford to be a legitimate drivetrain vendor to Olds I call it the Type F ten bolt. Olds service manuals refer to the Type B, O, P, C for the various corporate rear ends used in the 60s.

Here is what I use, and if you ever drag race or use sticky tires, it isn't so far from what you might choose:
Quick Perf. 9" housing, Moser 35 spline axles, Detroit Locker, Moser aluminum center, aluminum pinion support with 35 spline Pro gears and billet companion flange, original GM backing plates (opened from 2.87" to 3.15" hole for the bigger axle bearings) and drum brakes with G body aluminum drums, Velvetouch linings.

I know you stated street only, automatic trans, etc. If those parameters change, you will quickly move into needing more diff, and if you spent a lot of money on the 8.2, you would have to do it over.

47 Convertible

Located in Pacific NW north of Portland OR.
At this point in my 'education' on rear ends I'm leaning toward one of two options:
1. modify the 8.2 with Eaton posi, girdle, and new bearings/races as may be needed plus aftermarket axles if funds allow.
2. replace 8.2 with 8.5 posi in good condition if the 8.5 is pretty much a bolt in with not too many modifications.

I'd like to know more about how much would be involved to put the 8.5 in place of the 8.2. That would help me evaluate this option.
One article seemed to suggest the biggest factor was the 8.5 was an inch wider but everything else was pretty straight forward. I can handle the 1 inch wider but doubt that it could be as easy as a bolt-in deal.

Thanks again everyone for the information. It is really helpful
Jerry

507OLDS

An 8.5" 10-bolt would be nice.The challenge for that would be getting all of the brackets & perches on there correctly,like they did with your 8.2" 10-bolt. If you did go that route,get one from a 71-72 Cutlass/442,71-72 Skylark/GS,or you could get one from a 73-77 Cutlass or Skylark. Both of these styles have bolt-in axles,no c-clips.

47 Convertible

Sounds like it is time now to go to the local pick n' pull and scope out some of the mentioned vehicles and have a look at the rear ends to see how much work it would be. Thanks for the added information.
Jerry

monzaz

The PONTIAC 10 bolt 8.2 is the strongest of the 8.2 rears.
The MAIN BEARING caps are the thickest and widest of all the 10 bolt rears, EVEN the 8.5...Yes that is a FACT.
The spider gears will be your weak link in the pontiac and ALL other rear differential Open OR limited slip posi unit rears. The 4 pinion spider gear posi for PONTIAC or any other rear size is the BEST choice as it will deliver the torque through more contact area into the side gear then of coarse to the axle shaft.

NOW if you have a 'N' on the housing that designates a NODULAR housing making it a better stronger dense cast mix... So it is a KEEPER Pontiac housing. Plus having bolt in axles is pretty desire able too.

Width- Since it is a 1967 -1972 whether it is a Firebird or Tempest rear it will be 55 1/4 " wide which is the wider version already, so the 8.5 will be a direct same width rear from 1970-1981 Camaro, Firebird and Trans Am. They are still VERY plentiful and can still find some with good ratios and will be able to be upgraded to 30 spline fairly easy and cost effectively.
The advantage of the 8.5 is cheaper to build, better selection of posi units and wider range of ratios available. They can and will be stronger than your 8.2

NOW- the 8.2 you have under your car has a bracket for a pan bar and that is RIGHT WHERE the axle code is located at on Pontiac... WF or other.
The housing you have under the car is VERY clean and seems to look and work well. If you are street bound it will hold with out any issues.

I build a lot of them and have built some that were tested behind 455 olds and buick motors even at the track for some time in Nostalgic racing applications.

Eaton would be the best choice for the pontiac rear ...it is the best you can get - at this time and probably for a while.


Gear choices are 3.36 3.55 3.73 and 3.90 NEW.

If you have 3.23 you can not get the EATON posi unit it is for the 3.36 and steeper gearing.

Another advantage of the 8.5 is the 2.73 -5.57 on a EATON or TRUE TRAC posi unit...

Hope this info helps some more.
Jim

47 Convertible

Thanks for the information. I will repeat myself and say this is a great site with very helpful members. You have given me a lot to chew on. My limiting factors are money and time. I want to get this Olds on the ground and driving before I tackle the body work and the convertible top, interior etc. So the faster and quicker I can get a reliable posi rear working the better I can meet my goals.
As you say I have probably the best of the open 8.2 rear ends but a 3.23:1. It is bought and paid for. To keep my costs low and since I can't get an Eaton, I need the next best posi unit I can run in that rear end plus a cast girdle and I'm good to go assuming bearings are OK.
If I go for an 8.5 I have the cost of buying a decent unit with posi plus the time to fabricate the mounting brackets and spring pads etc and time to clean it up and paint. Seems like posi 8.5s around the Pacific NW are priced at $600 and up at the 2.7 and similar ratios and $800+ for 3.36 and lower and almost all one sees on CL are Chevy.
With all your information plus my own build considerations I'm leaning more strongly toward keeping what I have and fixing it up with the best posi that will fit plus the girdle and going for it.

What is your recommendation for the best non-Eaton posi that will fit in the WF 3.23 rear end?

Run to Rund

See if you already have the 4 spider posi. you will break spiders first, then axles, and as Monzaz said, the caps are probably OK so the girdle isn't necessary on that rear, especially with the spiders and axles as "fuses".
If you don't want to keep that rear, you could send the housing to Quick and they could build a 9" that would replace it as a bolt-in. Or, another shop could weld on the special bracket but Quick would be able to ensure there is no warpage from welding that would misalign the axles. Who knows if that was done on your 8.2 for that matter.
The 8.2 will probably hold up with street tires, no wheel hop, particularly if it has the good posi in it. There is a decent chance of that if it really came from a GTO.

monzaz

I think this might have been a posi and maybe blew up and an open was just installed to drive.

I say this because a 'N' housing is performance and I am pretty sure your going to get a posi with that Housing option...Ya know?

Wish we could get the axle tube code under that driver side bracket. Jim

ARE you absolute about that ratio? If you remove the cover the ratio will be on the outer diameter of the ring gear IE 13 42 (3.23) or 11 37 (3.36)

Might want to double check before buying ANY parts. Jim

47 Convertible

There is a WF on the drivers side rear of the axle tube. There is also a cast N on the upper left side of the housing.
Attached pic is from the seller re. your request.
Finally, I will pull the rear cover and look later today to see what is actually in there. No doubt should have done that first. Apologies.

I will get back to you as soon as I check the rear end. My continuing thanks for your help and all the others who have contributed to this thread. I learn something every day.
Jerry

47 Convertible

Definitely a 3.23 Open. See pics. What size posi carrier do I need to keep my current R&P?

lettering on ring gear: 42 13 GM 1 67 M O

Pretty cruddy in there. Could be a junkyard rear, however all of the teeth in the R&P look good. no nicks or broken things.

monzaz

I CERTAINLY HOPE YOU WERE NOT DRIVING THAT REAR!!!! THERE HAS NOT BEEN FLUID IN IT FOR QUITE SOME TIME!!!!

You will need to check all those teeth ... make sure the ring gear spins free clockwise and counter clock wise at least a full rotation feel for any binding. And for GOD's sake put some oil on those gears...LOL.

3.23 you will nned the carrier that fits 2.93 3.08 and 3.23 the mid series carrier...I AM not sure if the mid series carrier ever came in super duty posi (4 spider gear 4 pinion posi.)

So from the looks of the posi units for sale NONE are going to fit the 3.23 you have in the rear.

If it we me I would tear that rear end bearings and guts out clean the cavity with some kerosene and then put all new bearings in there. LOOKS pretty rusty and hard to believe they are going to last after you do get the car running. 85.00 gets you all the bearings seal crush sleeve gasket bearings and races...DONE.
Auburn posi unit HP unit 389.00 2.93-3.23 carrier NEW

BAck to the units for sale. Find out what size ring gear bolt holes those units are. 3/8 or 7 /16" IF they are 7 /16" they are only good for 7071 72 ring and pinion from the factory. Limited use.

The unit to the far right is a 2 pinion posi but appears not to be the same size, could be a trick on the eyes, even the carrier bearing seem to be bigger diameter and carrier taller...... I would need to see more of the holes and spline count of the unit... The whole body of the unit seems is bigger... BUT appears to be a factory unit NOT aftermarket.

I would say if all those units are the same height across the bearings as they sit on the table and he says they are pontiac the one on the right will be the one you need as its ring gear flange is one step down from the left 2 and will be the mid series you need.

JIm

47 Convertible

Jim, I am shocked you don't recognize the new-tech dry lube in the rear end. It is the very latest.

Nope, not driving. It is a project car and probably months away from being a driver and years away from being 'complete.'

Decision is made to not buy the used posi's, to stick to my 3 .23 gears and get the new Auburn posi which will fit in what I have. Would like to have done Eaton but they won't fit my setup.

I will clean everything out thoroughly, put all new bearings etc. in and run it without threshing it to death and see how it works out.

A couple of pics of 47 as I bought it in Myrtle Ck. Oregon and with interesting brake system I am adapting from a 73 Econoline plus my rebuilt 455 being test fitted. Other car is my 36 Chevy.

Thanks to all who contributed and schooled me in rear ends. I know a lot more now than I did at the start of the week.
Jerry

507OLDS

I did a rear like that last year,a BOP 8.2" with 3:23's,and I put an Auburn unit in it,so there is a unit that fits those gears.It's a $325.00-$350.00 unit.I favored the Eaton,but I don't think there was one available,or I would have installed one,or possibly the customer didn't want to spend the extra money for one.Do a complete disassembly,and chenge all the bearings.Make note of where you shims came from,so you can put them back where they came from.The only thing you will need to check or adjust is the backlash,when swapping the carriers.The pinion will retain the existing pinion shim under the large bearing.As long as you have a dial indicator to check backlash,you can do all of this yourself.
I did have a 3:23 4-pinion rear before,so those units exist,but I wouldn't bother looking for one.You can't get any parts for them,and they aren't as strong as some think.At least with the new Auburn,you can send it back to them for rebuilding,and there is a limited warranty.You won't be setting the world on fire at the dragstrip,so that unit will be fine for your application.The rear that I spoke of went into a 66 Cutlass convertible,with a 455.I replaced all the bearings,installed the Auburn unit,and installed new axles.

47 Convertible

I appreciate the advice Brian. I never got into a rear end in that detail but this one surely needs to be stripped down to the bare housing and everything cleaned and bearings, races etc. replaced and have it set up correctly.

I think this does it for me as far as this thread I started. It accomplished all I had hoped and then some. Those who started and operate it should be proud of their effort. A great bunch of members. Thanks to all,
Jerry

monzaz

Quoted -I did have a 3:23 4-pinion rear before,so those units exist,but I wouldn't bother looking for one.You can't get any parts for them,and they aren't as strong as some think.At least with the new Auburn,you can send it back to them for rebuilding,and there is a limited warranty.You won't be setting the world on fire at the dragstrip,so that unit will be fine for your application.The rear that I spoke of went into a 66 Cutlass convertible,with a 455.I replaced all the bearings,installed the Auburn unit,and installed new axles.

I have never run across a Pontiac 4 pinion 3.23 BUT I do know the 68-70 buick had a 3.23 3.42 unit that was 4 pinion BUT had the larger carrier hub on the driver side and the normal 10 bolt carrier bearing on the passenger side...NOW that can be retro fit into the Pontiac BUT again it has 7/16 ring gear bolt holes too. So you would need the 1970 71 72 gears from Pontiac to fit the carrier or a set of zoom conversion ring gear bolts.
BUT I guess that is not to say it does not exists...Just never personally seen one, pontiac / olds original any way.

Take care Guys/Gals , Jim