jo75olds

Summit seems to have a lacking of Rear End Pieces. So I need a place to find some parts to give the new 455 I have under the hood more kick!

I have a 1975 C Supreme, with a 10 Bolt, Non-Posi, with Highway Gears

I want to get a POSI unit, I was thinking any where from 3.90 - 4.10 Gears (The car is still my daily driver so I am a bit lost with this)

The car will be raced on the strip as well


Any ideas? And any one know where to get these parts, and what parts I should use?

Thanks,
Jim

joe_padavano

Your corporate 8.5" axle is very common, so parts are available anyplace. Try Summit/Jegs for starters. You will be hating life with 3.90 or higher gears in a daily driver unless you plan to install an overdrive trans.

billykissell

highway gears are higher than 3.90. i think you mean lower (higher number-lower gear)

joe_padavano

Yeah, I meant higher numerical. Sorry.

Rickman48

I had this discussion with my nephew, a while back.
He has a '69 Cutass S with a stroked 455 and a turbo 400 - quick street, and soon to make a pass or two at the strip.
My biggest concern was overall RPM going through the traps - should be under 6000 for an Olds.
My 396 BB chevelle wagon, T-400, w/3:55 posi went 13:53 @ 109.59 mph - stock converter and a 2+second 60 ft time, and still 6300 rpm w/ 26 in. tires!
Even though we settled on a 3:55 also, and he's got 28 in. tires and a holeshot converter, with the torque and horsepower he has, I feel he'll be over 6500 if it hooks!
Not real good with a stroker, or a basically stock 455!

jo75olds

This 455 is far from stock and pushing 500hp.

I plan on keeping it under 6 grand, shiftin between 5000 - 5500

as far as the tranny, its got a Hevy Duty Torque Converter and a Sports/ Drag Racing Shift Kit

as far as "Daily Driver", daily driving where I am consists of 3-4 Highways and your going between 40-85 most of the time

thanks for your input, wasn't sure if the axle was a "GM" axle or an "Oldsmobile" axle

Jim

2blu442

Jim, I agree with Joe and would be looking for something more like a 3.23 or 3.42, or go with the overdrive. If you spend a lot of time between 40 and 85 I think this would be more liveable. When I bought my 1970 442 it had a Chebby 12 bolt with 4.10 gears and a Super T10 4 speed. I used it as a daily driver in the 1990's and ended up putting in an overdrive transmission. I did not enjoy driving it on the freeway without the overdrive. My 2 cents worth! John

507OLDS

Summit has plenty of parts for that rear,as well as other vendors.That's a 71-up 8.5" 10-bolt,with 28-spline axles.I would put 3:73's in it.Driving will be managable,and it will keep you in the rpm range that you want for the strip.I run a 3:73 wiyth the 507,and I cross the line at 5800rpm,which is exactly where I want to be because that is where the engine makes peak power. Cruising at 60mph is about 2800rpm.

Rickman48

Brian - how tall a tire??
What MPH??

Run to Rund

507Olds knows those rear ends, and can sell parts or build one for you if you don't want to do it yourself, or don't want to hope you get the right parts when ordering from Summit, etc.

3.73 is a good compromise, but tire diameter matters too. 4.11 is good with tall tires, about 29", on the street and highway. The car will lose some pep with low numbers like 3.23 or 3.42, even with moderate tire diameter. I run 4.57 with a 30+ inch tire, 116 mph = 6000 rpm.

507OLDS

My tires are 325/50/15. 28" tall.I had to experiment with different converters as well.They can dictact 60fts as well as mph & rpm at the top. Once again,have a converter built for YOUR car,with YOUR drivetrain.Any converter you see in a magazine,is very vague,and usually designed for your typical smallblock Chevy.
She's gone 10:90's @ 122mph,but not a good street tune. The last few years that I ran my carb,I had a great street tune,& just ran it that way,no messing around,but went slower,but was also dead consistent.

jag1886

I just got a 3:90 gear, new posi unit and master install kit from www.ronsmachiningservice.net out of MI. He was a real nice guy and the whole thing was only 710.00 delivered. That was a lot less than I could find it other places.

507OLDS

Quick Performance sells units & kits on ebay,under the user name staticz,or something like that. You can get a posi unit,gears,and install kit,for $535.00. The posi unit is a Yukon,which is a copy of an Eaton,the gears were Yukon last time I checked.I don't remember what the install kit was,but you get what you pay for.I have my choices of what I use because its my *** if it fails,so I can't let the price dictate the job.I gotta use good stuff,and they cost what they cost.

ah64pilot

507, are you running a 12 bolt or Ford 9"? I am looking at building a 9" for my '72 Supreme because I don't wanna break anything at the track. I am hoping for low 11 sec times, we'll see. I'm not stroked but am running ported Edelbrock heads w/ a .552/.574 lift cam w/ 244/252 duration at .050", also KB IC886 flat tops on a decked block.

Do I need the 9" or would a 12 bolt w/ c clip elims do the job?

507OLDS

If your 72 Supreme still has the original 8.5" 10-bolt,I would use that.Build it with a good posi unit like an Eaton,or go with a Detroit Locker.Order a set of Moser 30-spline axles with 1/2" wheel studs,and top it off with an aluminum girdle support cover.That rear will handle it.I have built plenty of these,including the one under my own car,and it is still going today.I did however switch it to another car,but still taking that same amount of abuse.
If you want to see what is under my 72 now,go to the differential section,and look for my topic titled My "12-bolt". I really had no reason to build it,other than I just wanted to.

oldzy

I would do that as well, same as I did in my 8.5" 10-bolt. I changed to a Eaton 3-series posi, 30-spline Moser axles (I see the ends are rusting already just sitting there - will have to paint), and 3.42 Richmond 'Double Diamond' gears, all from Summit.

ah64pilot

The rearend I have now is an 8.5" 10 bolt with an Auburn locker and 3.42 Richmond gears. I haven't broken it yet but was afraid once I put the new motor in and start running slicks and low 11's it would bust.

If you are sure it would handle it I think I'll save the money and build it up a little more. I was gonna run 4.11's in the 9" so I'll just get a new set of gears for the 10 bolt, Moser axles, the girdle cover and keep the Auburn locker.

monzaz

WHAT were your plans on the 9" build? If you are planning on getting a STOCK center built, DUMP that idea it will not hold... GO aftermarket on everything or you will be sorry you did not.
Just run the 10 bolt 8.5 with upgrade parts. You know it is a good straight housing, and it will do the job with aftermarket parts.

Good luck on the choice. Jim J D

ah64pilot

I called a local shop (Pyle Brothers) and got an estimate of what it would cost to build my '72 10 bolt rear. They estimated $1300 for a Tru-Trac posi and 4:10 gears. I think that is a bit high...wouldn't it only cost a little bit more for a 12 bolt? I think I can get a 12 bolt housing for cheap and then have it built.

I also have a source for a $100 Oldsmobile 12 bolt complete rear end. Other than 10 bolts on the ring gear, what is the difference between this and a Chevy 12 bolt?

I just don't want to invest $1300 in a 10 bolt when I could spend $1600 and get a 12 bolt. Any advice I can get, including a cheaper builder would be appreciated!

oldzy

FWIW, I spent $700 on just labor alone, and ~$2000 (not incl. tax or shipping charges) on parts. It really broke me for a while. All that... and my pinion seal leaks like crazy.

507OLDS

The Tru-Tracs,with the helical gears,are intended more for the road course guys,and very limited dragstrip. I would do a tuned Eaton unit,or a Detroit Locker. The Moser axles,with 1/2"x3" wheel studs,HD retainer plates,and beaings/seals installed,will be about $480.00-$500.00 once they are at your door.The Detroit Lockers are $620.00 to your door.A tuned Eaton posi unit would be $550.00 to your door.
With your existing set-up that you have now,the Auburn unit is the weak link.Those are great units for cruisers & mild builds,but not big-torque,trans-brake,or stick-shift applications.

ah64pilot

Hey Brian, how difficult do you think it would be for someone with a lot of mechanical know how to build a rear end? I have never opened one up before but I have a lot of years doing this and even more experience repairing turbine engines on the Apache helicopter. I'm no dummy, just need good instructions...doable? I'm trying to save money where I can.

507OLDS

If you have the patience & mechanical ability,you can do it.The end result is that you need a good pattern on the gears.You will need a dial indicator to measure the backlash,and access to bearing pullers/presses.

ah64pilot

Ok, scratch that idea...I'd spend as much money getting the tooling as I would in labor, might as well KNOW it's done right haha!

I found a 12 bolt housing on Craigslist with casting numbers 402227 CFD8, isn't that an Oldsmobile non W-27 housing with 10 bolt internals? If so the guy is asking $375...rip off!

507OLDS

Yes,that is a 12-bolt O-axle housing.

ah64pilot

Ok, I found a complete 12 bolt in a Monte Carlo (don't know ratio or if it's open or posi. Also don't know axle size)...guy is asking $600, reputable guy I've done business with before. Is $600 a good price?

RhinoGTO

Brian, I have a '72 cutlass S, 350. I am looking to swap to 3:73 gears. It currently has 2:73 open rear. Im assuming its a 8.5" 10 bolt? (its original) as far as I can tell. The car is mainly street driven and might see the track rarely. I plan on rebuilding the 350 or maybe going with a mild 455 in the future. What would you recommend for rebuilding the rear? I would imagine I won't ever see more than 300 rwhp. Thanks!

507OLDS

ah64pilot,
$600.00 for the 12-bolt chevy core is pushing it,if it has your typical 2:56 or 2:73 gears,and non-posi. If it is a 3:31 non-posi,that would be worth the $600.00,even if you don't want that gear.They do not make the 3:31 gear in the aftermarket,and the good used GM 3:31's usually bring $100.00 or better,so you could make some money back.The ratio codes on the 12-bolt Chevy rears are on the frontside of the passenger axle tube,exactly where they are on the 71-72 8.5" 10-bolts.If you can get the codes,I can tell you what should be in there,or what was in there originally.

RhinoGTO,
Your existing rear will be fine.Install a posi,gears,and replace all the bearing/seals.Your existing axles shafts will be fine.

ah64pilot

Thanks for all your help Brian, I've decided to go with your original advice and build up the 8.5" 10 bolt that's in the car. My budget just got cut by $3000 so a trick rear end is no longer an option, no pun intended by the way.

After reading something you wrote about crossing the line at 5800 RPM w/ a 3.73 gear I've decided I'm gonna go with an Eaton posi, Richmond 3.90 gears (rather than 4.10), and the Moser axles.

I assume I will have to order the custom length axles from Moser? Or do you have a part number for these parts to make it easy? Lol! I feel like I'm abusing you, but I really do appreciate it!

Steve

507OLDS

Steve,
I order those axles a lot,so I have a spec sheet,with all the dimensions.I can fax it to you or something.

ah64pilot

Email me if you can...check PM

jo75olds

Thanks Brian...The engine is a 455 + .030 with K-B ICON piston, Eagle H-beam rods, Edelbrock Performer RPM heads, Comp Cams XE274H cam (230*/236* @.050- .520/.523" 110* Lobe Sep) and I am HOPING to be able to fit the Edelbrock Perf. RPM Air Gap Manifold.... Should be making Max torq around 4K RPM (aprox 560ftLbs..) on Computer Dyno...looking at 510 HP @5000 & 490 FtLbs @2000RPM...The Engine is in the Machine shop for the bore & mains alinge bore, deck clean up & crank grind,polish & balance...(any Harmonic Balancer recomendations?) We are opening the main bearing clearances a bit, I have read that the main webs tend to "walk" a bit so I am figuring a .0035 mains clearance. Also...ARP studs or bolts on the mains? Have not made rocker arm choose yet...Comp Cams Roller...or Harland Sharp Roller???

Turbo 350 with B&M Shiftkit, and a BIG tranny cooler, and a Hughs 2500-2800rpm BOP Heavy Duty Converter (converter gives me 2700 with foot brake & my stock 350C.I. 1975 smog engine ...I know that the Tranny is the weak link right now...but it has a fresh set of clutches,bands & the shift kit, so I am keeping my fingers crossed... and we will be running the stock HEI from the '75 350 engine. Running BFG T/A radials..275/60 15 (28") on the street. Hope to get some slicks for the track....

So do you think the Eaton "Posi Performance" unit with carbon clutch pak is a stronger and safer bet then Eatons Detroit TrueTrac. I am on a limited budget..my Dad is helping out (his componant choses), but we are not "High Dollor" guys.
Will the 28 spline axles hold up??? ANY SUGGETIONS for this setup?? planing on a 870 CFM Vac secondery carb..Probably get the Holly Street Avenger, and a set of Headers (any suggetions hear also???) My Pop used to run Chevy small blocks in C2 Corvette & a 1970 Camaro SS...But this is new to him & he hasn't built a car in 30 yrs...
SORRY for the long post...just figured it might help you evaluate my setup....OPENED TO ALL SUGGETIONS!!!
MANY THANKS!!!
Jim

Aceshigh

.....and you want 3.90's with a 3 speed trans......when premium is almost $5 a gallon.

This is entertaining. I think you need to re-evaluate your plans and understand what you're getting into here.


Exactly why you need to re-evaluate your plans. They're full of fail to your wallet with gas prices in a DD>

507OLDS

If this is a daily driver,and you are doing highway driving,the most gear I would put in it is 3:42's.It will hurt the track performance a bit,but the overall driveability will be better.If it was a street/strip application,with very little or no highway driving,then you could do a 3:73.That is all that BBO would need.
ATI makes a great harmonic balancer.They use a 3-bolt pattern for the pulley,so you will need to drill 2 holes in your existing pulley.One of the original holes will work.
Harland sharp rockers.
The TH350 is not a weak link,but a B&M shift kit can be.My friend's 71 goes mid-11's all day,with a stout BBO,TH350.
A hot HEI is fine.Put the lightest springs on the weights,and do not hook-up the vacuum advance.Let it advance itself mechanically.Gap the plugs at .045" to start,and go from there,unless you are running an MSD box with it,then the gap needs to be smaller.
The stock axles will be fine.The Eaton unit is a better suit for your application,compared to the Tru-Trac.
The 3310 Holley 750 vac secondary carb has always worked well for me on a street 455. The chokeless Holley 830 DP would be a step above.
Technology has come a long way in 30yrs,and you are not building a Chevy.You are doing research & gaining knowledge.Nothing wrong with that.

tocicar8825

I know this is an old thread. I've tried to read as much as I can find on what diff I can use in my 442. Here is what I've got: 69 - 442 with a 12 bolt. I've not had it open yet, but it is an open carrier - not a posi - I guess it could be a broken posi?. Looking at different diffs to use, I like the look of the performance of Eaton Detroit Truetrac Differential 913A555. Looks like a good strong limited slip differential. Question is when I go to Jeggs site to look at it, they show it fits a 64-70 Olds as well as a Ponco and Chevy. 30 spline axles. From what I've read my rear should have a 28 spline axles. I have to guess that the Eaton carrier accepts a 30 spline and my axles are 28 spline - and Jeggs just has the wrong info down on their site. Summit only list thiis posi diff for my car: Yukon Gear & Axle Dura Grip Positraction Carriers YDGGM8.2BOP-3-28-1
I want the best posi for the best price (don't want much do I?). My Olds has a 425 in it, mild cam, Performer intake and 750 carb. Headers and a MSD ignition. I don't use the car for strip racing, but for just for fun. Hard to make it hook up with the combo I have now (4 speed tranny). Not sure of my gear ratio - and I don't have a working tach yet - but it accelerates like a bat out of hell. SO - 28 spline in the 69 12 bolt carrier? Thanks - Rocket Head Ed

joe_padavano

First, you don't have a 12-bolt, despite the number of bolts on the back cover. Unless your car was built in Canada or the axle was swapped, it has a Type O rear axle, with only ten bolts holding an 8.5" ring gear to the carrier. This axle was only used in 1967-1970 Cutlass and 442 cars. It was NEVER used in any other GMs, so your first clue is that anything that says "also fits Pontiac, Chevy, or Buick" means that it will NOT fit this axle. Parts for the Type O are nearly nonexistent, don't interchange with any other GM axles, and I can guarantee that you won't find them in the Summit or Jegs catalogs.

tocicar8825

Hi Joe:
So there aren't any units on the market that can bolt into the stock unit's place in the carrier? I found this one made by Standard Gear: http://www.quickperformance.com/ZP-P...-_p_15732.html
base on a post from another thread that led me to Ron's Machine Shop. If the above unit doesn't work in the O rear - what is my best option? My rear end is shot - not broken yet, but worn out. Thanks

joe_padavano

Yes, I believe that will fit the Type O. Most of these are converted Ford units. Others here are better versed on that.