12 Bolt Rebuild - Team Camaro Tech
Transmission & Driveline Transmissions and Differentials

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  • 1 Post By Chevy68
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post #1 of 15 (permalink) Old Feb 3rd, 20, 07:27 PM Thread Starter
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Jeff
 
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12 Bolt Rebuild

Going to rebuild my 12 bolt posi. Looked at buying parts for my carrier, (clutches, side gears and spiders) then I found this Yukon kit, what is everyone’s thoughts?
https://www.ebay.com/itm/GM-8-875-Ch...ry!77365!US!-1
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Thanks,

Jeff


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post #2 of 15 (permalink) Old Feb 4th, 20, 05:34 AM
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Re: 12 Bolt Rebuild

Your old Eaton Posi is stronger than the Yukon Dura Grip. I'd recondition it and keep it. If the parts in your Eaton are still good then there is no need to replace them. Many times all you need to do is shim the clutches to restore the preload.

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post #3 of 15 (permalink) Old Feb 4th, 20, 06:03 AM
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Re: 12 Bolt Rebuild

Why a rebuild? Jack up one wheel of rear axle, leave trans in neutral.
Apply torque wrench onto a lug nut and rotate the one tire with opposite tire on the ground.
You are testing the tightness of the clutches. Torque to 'break loose' the clutches is a minimum of 35 ft-lbs.
If the axle passes this test, just change oil and add GM clutch additive.
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post #4 of 15 (permalink) Old Feb 4th, 20, 07:09 AM
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Re: 12 Bolt Rebuild

Don’t over do the Posi additive. It can get too slippery and interfere with the clutch lock up.

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post #5 of 15 (permalink) Old Feb 4th, 20, 10:39 AM
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Re: 12 Bolt Rebuild

Just install heavier springs. Standard rate for the springs is 50 lbs/inch. GM sells, or used to, 75 lb springs.
I would like to say, yellow springs are standard and green are heavier rate.

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post #6 of 15 (permalink) Old Feb 4th, 20, 04:24 PM
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Re: 12 Bolt Rebuild

I agree with the spring change
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post #7 of 15 (permalink) Old Feb 4th, 20, 04:44 PM
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Re: 12 Bolt Rebuild

You don't need heavier springs if the clutches are good and shimmed correctly.
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post #8 of 15 (permalink) Old Feb 4th, 20, 04:57 PM
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Re: 12 Bolt Rebuild

Quote:
Originally Posted by Everett#2390 View Post
Why a rebuild? Jack up one wheel of rear axle, leave trans in neutral.
Apply torque wrench onto a lug nut and rotate the one tire with opposite tire on the ground.
You are testing the tightness of the clutches. Torque to 'break loose' the clutches is a minimum of 35 ft-lbs.
If the axle passes this test, just change oil and add GM clutch additive.
Everett, What a great tip. I might be tipping my knowledge (or lack of it) but I had never heard of that. I will go try it out on my newly installed used 12 bolt as soon as I can.
Thanks,

Brett......

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post #9 of 15 (permalink) Old Feb 4th, 20, 08:17 PM Thread Starter
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Re: 12 Bolt Rebuild

Thanks Freddie, that what I was thinking that the Eaton unit was superior.

It always starts off as a simple project. had leaky axle seal, changed bearings and seals. Thrust washer fell out trying to install pin. Noticed pitting on the spider and side gears and what looks like debris marks on both sides of the thrust washers. Current plan is to pull the carrier and clean and inspect everything.

Just exploring options and best route once the inspection is completed.

Everett, thanks for the tip on using a torque wrench.

Thanks,

Jeff


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post #10 of 15 (permalink) Old Feb 5th, 20, 07:14 AM
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Re: 12 Bolt Rebuild

You're welcome, straight from the Chevrolet Service Manual
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post #11 of 15 (permalink) Old Feb 5th, 20, 08:48 AM
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Re: 12 Bolt Rebuild

I went with the Yukon set up and axles and it turns out that the axles have a larger inner stand-off than mosier, strange or stock replacements so I had to get my rotors machined. Then I had to get the caliper brackets machined since the axles stick out slightly further than the aforementioned brands. Not the end of the world but it was annoying.
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post #12 of 15 (permalink) Old Feb 5th, 20, 09:02 AM
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Re: 12 Bolt Rebuild

I have this on file, shows how to rebuild a Eaton posi, he also sells all the parts needed to rebuild.
Good video to know the inner workings.
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post #13 of 15 (permalink) Old Feb 5th, 20, 12:13 PM
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Re: 12 Bolt Rebuild

Quote:
Originally Posted by Everett#2390 View Post
You're welcome, straight from the Chevrolet Service Manual
Quote:
Originally Posted by Everett#2390 View Post
Why a rebuild? Jack up one wheel of rear axle, leave trans in neutral.
Apply torque wrench onto a lug nut and rotate the one tire with opposite tire on the ground.
You are testing the tightness of the clutches. Torque to 'break loose' the clutches is a minimum of 35 ft-lbs.
If the axle passes this test, just change oil and add GM clutch additive.
I never knew those specs existed!

Chevy68, be aware that a special tool is used in the service manual to attach the torque wrench in the center of the hub. You should be able get accurate readings if you orient the wrench at a tangent to the hub, (90 degrees from the centers of the hub and the stud.)

Just in case you weren't aware...
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Last edited by 69-er; Feb 5th, 20 at 07:12 PM.
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post #14 of 15 (permalink) Old Feb 5th, 20, 07:10 PM Thread Starter
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Re: 12 Bolt Rebuild

Quote:
Originally Posted by AZ_Bill View Post
I went with the Yukon set up and axles and it turns out that the axles have a larger inner stand-off than mosier, strange or stock replacements so I had to get my rotors machined. Then I had to get the caliper brackets machined since the axles stick out slightly further than the aforementioned brands. Not the end of the world but it was annoying.
Funny how these simple little project turn into big projects!!!

Thanks,

Jeff


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post #15 of 15 (permalink) Old Feb 5th, 20, 07:12 PM Thread Starter
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Jeff
 
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Re: 12 Bolt Rebuild

Quote:
Originally Posted by 69-er View Post
I never knew those specs existed!

Chevy68, be aware that a special tool is used in the service manual to attach the torque wrench in the center of the hub. You should be able get accurate readings if you orient the wrench at a tangent to the hub, (90 degrees from the centers of the hub and the stud.)

Just in case you aren't aware...
Thanks for the heads up. I do have a 3- hole puller I could use to center on he hub.

Thanks,

Jeff


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