12 bolt rear end rebuild

[samhart]

i had a 9 second mustang that i just sold. i thought long and hard on what my next project would be and i chose a 72 chevy truck. i bought a frame that came with a 12 bolt. i helped my friend rebuild his 9 inch, but obviously this is a whole different animal. i guess what i am getting at is i am not completely ignorant when it comes to rebuilding one, yet i would like to have some literature to be able to read through as i am doing it. i haven't even torn into this thing yet, but i know it is going to be alot different not being able to take out the pig and all. i haven't had too much luck locating any manuals, and was just wondering if anyone had any books that they would suggest, and where i can buy them. thanks

[JimKshortstep4x4]

Welcome to the board from West Michigan!

The truck overhaul manuals have a good section in them on the 12 bolt rear and the 67 truck version is available at this site:

http://www.gregsonline.com/

Manuals do come up for sale and you may be able to find a used one for your year truck.

Jim

[samhart]

thanks alot for your help

[KFreddy]

I just had my 12 bolt rebuilt, it was originally a one wheel peel. I got my parts from DTS in Michigian here is a web site drivetrainspecialists.com These guys were all over it answering questions before i even had a chance to ask them Here is the part list that I used to convert to a posi rear end,

Gm 8.875 bearing kit
Eaton series 3 carrier
GM 3.08 ring and pinion
12 Bolt Truck Aluminum Cover

Installation was relativly simple, all the parts were there and complete

Good luck,

-Fred

[Already Gone]

Originally Posted by KFreddy

I just had my 12 bolt rebuilt, it was originally a one wheel peel. I got my parts from DTS in Michigian here is a web site drivetrainspecialists.com These guys were all over it answering questions before i even had a chance to ask them Here is the part list that I used to convert to a posi rear end,

Gm 8.875 bearing kit
Eaton series 3 carrier
GM 3.08 ring and pinion
12 Bolt Truck Aluminum Cover

Installation was relativly simple, all the parts were there and complete

Good luck,

-Fred

Was that the original rear end in your truck and did you use your original axles ?

[samhart]

i really do appreciate the help.......i ordered the book jim. the website is now in my favorites fred.

[Psycho71]

Also, check out Richmond's and other gear manufacturers websites. Look for their instructions on setting up the gears. I printed out about three sets of them from different sites, looked over them for a couple of nights, and dove in. It all went pretty smooth. But I had the rear end out of the truck too. It would have sucked trying to do my first one while in the truck, that's where that 9" comes in handy.

[KFreddy]

Greg,

Yikes don't remind me, yes the original axels, 6 cylinder truck with a 12 bolt rear, with a bit of prayer and some duck tape I might be in the clear

[Imperial Kustom]

Hey guys, guess what my day job is!? I rebuild rerends at Jim's Drivetrain Specialties here in Boise, Idaho. I dont see what all the fuss is about over using your stock axles KFreddy. As long as they arent bent, flaking or grooved, you're good to go. There is no difference in the internals of a 12 bolt between motors. As far as rebuilding these goes, it is a fairly straight forward deal. Some important guidelines to remember, whether you know or not.
Never mix your caps side to side.
Don't over crush the crush sleeve. It's only a matter of inch-pounds of preload on the pinion bearings that you want.
Especially if you switch gears or the carrier, the side shims usually won't fit correctly in their respective positions. when you order parts, ask for some "Super Shims". These are stackable shims and make this step really easy.
The side shims should just fit snugly into the housing, tight enough though that a hammer is required to tap them all the way in. You should not be able to remove the carrier by hand.
Always re-use the stock pinion shim (if it is in good shape).
Backlash on these should be .008-.012., and everything should spin with some resistance and quietly.
Keep all this crap in mind, and it should go really smooth.

[Already Gone]

Originally Posted by Imperial Kustom

Hey guys, guess what my day job is!? I rebuild rerends at Jim's Drivetrain Specialties here in Boise, Idaho. I dont see what all the fuss is about over using your stock axles KFreddy. As long as they arent bent, flaking or grooved, you're good to go. There is no difference in the internals of a 12 bolt between motors. As far as rebuilding these goes, it is a fairly straight forward deal. Some important guidelines to remember, whether you know or not.
Never mix your caps side to side.
Don't over crush the crush sleeve. It's only a matter of inch-pounds of preload on the pinion bearings that you want.
Especially if you switch gears or the carrier, the side shims usually won't fit correctly in their respective positions. when you order parts, ask for some "Super Shims". These are stackable shims and make this step really easy.
The side shims should just fit snugly into the housing, tight enough though that a hammer is required to tap them all the way in. You should not be able to remove the carrier by hand.
Always re-use the stock pinion shim (if it is in good shape).
Backlash on these should be .008-.012., and everything should spin with some resistance and quietly.
Keep all this crap in mind, and it should go really smooth.

Thanks for your input. I will probably get someone to assemble the axle for me. I was more thinking about the extra cost of new axles if the old ones wouldn't do. I bought a used 12 bolt differential with the saddles and no guts at all , just the housing, from a wrecker and want to use it for my new gears. That way I can just sell my stock 3:73 rear end to someone that needs it and the only downtime for my truck will be during switchover.

[N2TRUX]

Originally Posted by Imperial Kustom

Hey guys, guess what my day job is!? I rebuild rerends at Jim's Drivetrain Specialties here in Boise, Idaho.....

How about writing a nice FAQ with pics? We could host it in our FAQ forum so next time someone asks...

[crakarjax]

The closest I could find to a rebuild guide is an article from "Chevy Punch" but it is for a car 12-bolt. Probably the same exact procedure though. I attached the pdf for reference.

Edit: the file is way too big for the tiny filesize limits here, so here is a direct link!
http://www.chevypunch.com/issues/march2007.pdf

[mnunn454]

Check out www.chevelles.com for their on-line monthly mag called Chevy Punch".

This month was all about setting up a 12-bolt.

I think you'd find it helpful.

[crakarjax]

Awesome (really old) thread! I was surprised to come up with very few good posts about rebuilding the 12 bolt. Any new info/resources out there? I see rebuild kits on ebay for like $90 shipped with koyo(?) bearings, are they any good?