10 Bolt 8.5 I.D. Help

Old March 16th, 2019, 10:44 AM
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10 Bolt 8.5 I.D. Help

I have a 1971 Cutlass Supreme with what appears to be a GM 10 bolt 8.5 rear. I'd like to know what the carrier and gears are, based on the axle stamp.

Any help would be greatly appreciated!


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Old March 16th, 2019, 12:45 PM
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If it hasn't been messed with the R2 code is for a 2.56 open carrier.
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Old March 16th, 2019, 12:56 PM
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2.56 open is the base no-cost option axle.
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Old March 16th, 2019, 02:05 PM
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Thanks for the info!

I'd like to convert to posi with higher gearing, - i'm thinking 3.23 or 3.08?

Looking for some gearing and posi carrier recommendations. My current setup is:

350 stock rebuild 10k miles ago/ dual exhaust/ Qjet 4bb/ Edelbrock 2711 performer / Thorton exhaust manifolds. I'm planning on changing the camshaft at some point
TH350 very recently rebuilt mild street/ strip with a 2200 converter

I typically do all of my own work, but i'm considering having the carrier and gearing change done. Any recommendations on someone in Connecticut who is good?

Thanks,
J
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Old March 17th, 2019, 06:11 PM
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Engine options gear ratio

I have a web site set for people that want to give it a shot. Parts I think we had posi rebuild kit and gear pacakage deals or it could have been on V8 buick.com... Have to look in the for sale section.
search 8.5 gear posi something like that.
Yukon Posi
Yukon gears and rebuild kits.
As far as the ratios your picking good stuff...BUT do not up the cam too much stay in the 260 -268 advertised cams for the 350 cube as it will produce the most torque and that is really what makes a muscle car FUN to drive. Please do not get hung up on the HP numbers because that usually does not happen till way up in the RPM range that most cars do not get to unless your at the track.
300HP does not sound cool BUT the quick torque a 300HP cam will be WAY fun with 2200 stall...

Oh and getting even stock heads with good valve work done...NOT even porting JUST a good valve job goes a long way to waking up a motor. Do a compression check on the motor and see where your pressure is at and pick a cam that will work with that pressure. Too much duration on a low compression motor will JUST KILL your low end torque.
Have fun. Jim
J D

Last edited by monzaz; March 17th, 2019 at 06:13 PM.
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Old March 17th, 2019, 06:14 PM
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That is a 10 bolt 8.5 Oldsmobile for sure. Should be easy to get any ratio posi etc.
Jim
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Old March 18th, 2019, 08:50 AM
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Originally Posted by monzaz View Post
I have a web site set for people that want to give it a shot. Parts I think we had posi rebuild kit and gear pacakage deals or it could have been on V8 buick.com... Have to look in the for sale section.
search 8.5 gear posi something like that.
Yukon Posi
Yukon gears and rebuild kits.
As far as the ratios your picking good stuff...BUT do not up the cam too much stay in the 260 -268 advertised cams for the 350 cube as it will produce the most torque and that is really what makes a muscle car FUN to drive. Please do not get hung up on the HP numbers because that usually does not happen till way up in the RPM range that most cars do not get to unless your at the track.
300HP does not sound cool BUT the quick torque a 300HP cam will be WAY fun with 2200 stall...

Oh and getting even stock heads with good valve work done...NOT even porting JUST a good valve job goes a long way to waking up a motor. Do a compression check on the motor and see where your pressure is at and pick a cam that will work with that pressure. Too much duration on a low compression motor will JUST KILL your low end torque.
Have fun. Jim
J D
Great info, - I really appreciate the detailed response, - thanks Jim!

I found the items on your website. I'll watch a couple of youtube videos, and consider doing the job myself. I'll definitely be contacting you to purchase the carrier, gears, and rebuild kit

Thanks,
John

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Old March 18th, 2019, 04:49 PM
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you tube videos

Please all be careful on the videos out there...lol. THAT is why I am so busy.... too many people making videos thinking they know what they are doing. If I have time it is a good laugh for an evening.

Sometimes it is better not to have ANY info than bad info filling the mind.

Jim
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