Looking at buying a 70's model O-type 12 bolt posi rear end with 3:08 gears. Are parts readily available still for this rear end? Posi rebuild kit if needed, can I purchase some 3:42 gears if needed.

Going in a 71 convertible with 350 engine and 350 turbo transmission. This car is driven with a car club and we do drive them sometimes as far as 200 miles or so.

 

From my understanding, gears are not currently being made for the olds 12 bolt. Good used or nos are scarse. I believe you can rebuild the posi and even get a ford 8.8 posi that has been machined to fit/ gears to bolt on for the rear

 

Twenty whole miles, huh? Heck, you can push the car that far.

As for finding out about Type O axles, go to SEARCH and type in "type o" axle (with the quotes as I've shown them). You'll get many, MANY threads about this topic.

 

If you change from the '71 corporate rear end to the O-type (12-bolt cover, 10-bolt gear); you'll need a different driveshaft.

As far as I know, Supercars Unlimited (some people like SU, some people hate 'em) has a lot of options for the O-type rear.

Steve

 

By the way, since no one else has said it yet, the Type O axle ISN'T a "12 bolt" axle. It only uses an 8.5" ring gear held on with ten bolts. Do not equate bolts on the cover to what's actually inside the axle.

While the parts don't interchange, that's the same as the 8.5" ring gear in your current 1971 axle. Parts availability for the corporate 10-bolt is infinitely better than for the Type O. This change doesn't make any sense.

 

New 3.42 gears at Summit Racing.

http://www.summitracing.com/parts/rmg-4900491

3.90 also available.

http://www.summitracing.com/parts/rmg-4900501

These gears are specifically made to fit the posi unit in the 3.08 rear you are looking at.

 

Is Richmond actually making these again, or is this a listing for parts that cannot be delivered?

 

Joe, it says ship date today so looks to be available. One quick call to Summit would verify that.

 

My convertible actually already has the 12 bolt Oldsmobile with the boxed control arms and sway bar ( 12 bolts on the cover ). But it has, I am guessing a 2.?? something gear. I will climb under the car tonight and see what info is stamped on the axle tube.

 

The factory 1970 carriers are:
2.56-2.78(673)
2.93-3.23(671)
3.42up(588)

The Richmond gears are made to fit the(671) 3.08-3.23 carrier.

Factory 1970 carriers:
673______1967-1970 2.56-2.78 28 spline axles

671______1967-1970 3.08-3.23 28 spline axles

588______1967-1970 3.42-5.00 28 spline axles

 

There is no 2.93 ratio in the 12 'O' rear 3.08 3.23
2.56-2.78(673) 28 spline axles
3.08-3.23(671) 28 spline axles <<< Richmond gears fit this carrier ONLY!
3.42-5.00 (588) 28 spline axles
3.42-5.00 (672) 31 spline axles

We have posi carriers if you need and rebuild kit and gears too. Sometimes we have reconditioned posi units also. JIm
J D

 

Oh by the way the parts for the 8.5 are available too I give all the forum here the deals best I can. Take care, Jim

 

Note that these are the posi carrier numbers. There are also non-posi carriers for the same gear ratios.

 

Might be out of my realm but..... My '70 442 was a 3:23 one wheel wonder...bought a posi (3:23) unit from Supercars Unlimited. Very happy with it running for the past 3 years about 3000 miles so far....
Got lucky when installing it only had to take it out once to shim for backlash. By the way my kitchen island worked well as a surface plate for measuring for correct shims (which was included). It's the quartz material and flat within .0005" (yes I was a machinist for 10 years) and of course not married...just haven't found the woman that would let me use the kitchen island as a surface plate yet !
Good luck! Also I have video of checking backlash if you want to see it send me your e-mail address.. mine is r.nagel.jr@comcast.net

 

2.56-2.78(673)
3.08-3.23(671) - no 2.93 in this rear. :0) Small technicality
3.42 -up(588)

We can make the 1969 and 1970 rears with 31 spline axles and you can retro fit the 672 carrier into the 69 70 housing IF you want...

Just wanted to keep that option open.

Jim
J D

 

Today I saw a "176" ?? open carrier from the '68 Type-O 12-bolt I think....


Who has the list of numbers on OPEN carriers, to flesh out this info a bit? Is it just the last 3 digits of the GM PN, 'cause I can do that myself.

 

The only open carrier number I have in my database is #156 = 3:08/3:23 open.
Good question about the PN. Since we already know the posi carrier casting numbers, can you check them against the GM PNs to see if the theory holds?

 

I have a 2 series open carrier number 358

394139 is the 12 bolt olds 31 spline casting for the center.
402227 12 bolt olds 28 spline casting Big M in the middle of the casting

Jim
J D

 

having your 671 posi with 3.08, you could you could put a parts wanted add here for a 3.23 open... just to get the gears that will interchange with that 671 and have a nice set-up.

 

or i could buy the 671 fom you

 

Cutlassdrop what exactly is wrong with the rear end you have right now? IMO you are better off getting the parts from monzaz and rebuilding the 71 rear end.

 

monzaz---

can you tell us about the ford posi carrier conversion? I have the O type in my 70 442 and want a posi and gears, about 391s would be great....thanks,cameron

 

Joe you should run across the bridge and see if speed unlimited has them LOL

 

I have a #588 factory posi that I just went through yesterday and OE 3:90 gears in nice condition that I'm going to list on here later with pics

 

What are you going to ask for them?

 

Kind of old why did you not start a NEW thread?

 

To Orange442 all the info should be in the classified section now.To Monzaz,I'm new to the site and didn't realize until it was too late,SORRY. This was the page that showed up when I did a search for this web site,