70 o-type 12 bolt rear end
#1
70 o-type 12 bolt rear end
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.
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.
Last edited by 71cutlassdroptop; December 1st, 2014 at 09:07 AM.
#2
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
#3
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 20 miles or so.
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 20 miles or so.
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.
#4
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.
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
#5
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.
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.
#6
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.
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.
Last edited by orange442; December 1st, 2014 at 08:51 AM.
#8
#9
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.
Last edited by 71cutlassdroptop; December 1st, 2014 at 09:17 AM.
#10
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
Last edited by orange442; December 1st, 2014 at 09:29 AM.
#11
correction
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
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
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
Last edited by monzaz; December 2nd, 2014 at 04:15 AM.
#13
#14
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
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
#15
Adds and corrections
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
#16
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.
#17
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?
#18
casting numbers
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
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
#25
#27
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,
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