12 bolt rebuild + eaton

[DavidB]

About four years ago I did a LS engine swap on this truck and have done way too many single tire burn outs and have been wanting to do a good posi ever since.
I have set up about a dozen rear ends and have never had a noise or problem with any of them (knock on wood). I'm going to do a simple how to on this with pictures to hopefully help some one here out. I'm no expert and any input is welcome.
The first thing you will notice when ordering parts is there is a 3 or 4 series. The 3 series is for 2.76 - 3.42 gear ratio and the 4 series is for 3.73 up. The difference is the thickness of the diff. The 3 series eaton is cheaper than the 4and you can order a "thick" 3.73 up gear to go on the 3 series.
My truck came with a 4 series 3.73 but since I'm doing a complete rebuild I orderd:
3 series eaton #19587-010 $425 Ebay
Motive gear thick 3.73 #mgr-gm12-3.73x $169 summit
rebuild kit # rat-3005k $109 summit
I decided to do the 3 series so I had the option of running any ratio with out replacing the most expensive piece.

[IMG]http://i859.photobucket.com/albums/ab159/dbright78/rearend037.jpg[/IMG]

[gcburdic]

okay David....I'll be following along.... to the boards from NC

[lyrikz]

Originally Posted by DavidB

About four years ago I did a LS engine swap on this truck and have done way too many single tire burn outs and have been wanting to do a good posi ever since.
I have set up about a dozen rear ends and have never had a noise or problem with any of them (knock on wood). I'm going to do a simple how to on this with pictures to hopefully help some one here out. I'm no expert and any input is welcome.
The first thing you will notice when ordering parts is there is a 3 or 4 series. The 3 series is for 2.76 - 3.42 gear ratio and the 4 series is for 3.73 up. The difference is the thickness of the diff. The 3 series eaton is cheaper than the 4and you can order a "thick" 3.73 up gear to go on the 3 series.
My truck came with a 4 series 3.73 but since I'm doing a complete rebuild I orderd:
3 series eaton #19587-010 $425 Ebay
Motive gear thick 3.73 #mgr-gm12-3.73x $169 summit
rebuild kit # rat-3005k $109 summit
I decided to do the 3 series so I had the option of running any ratio with out replacing the most expensive piece.

[IMG]http://i859.photobucket.com/albums/ab159/dbright78/rearend037.jpg[/IMG]

ohhhhhhhhhh. im in.. More more more. I have a 12bolt single legger attached to my 454. ahha..

[hjewell2]

Yes please do one I'm IN I'M IN Getting ready to do one this fall, Series 4 with 4.10 gears 28inch tall tires. Right now it has a open diffy sreies 3- 3.08

My biggest concern if I'am correct is with the shim behind the pinion bearing.
I hate the thought of pressing the bearing on and off until I get the right shim in place.

[eightbanger]

It's weird how this works sometimes, I've already got a posi with 4.11's but am in bad need of a rebuild, and just got round to asking the tech guys at Drivetrain.com what I need, and they just sent me the details today
I was going to start the tedious task of searching the net for 12 bolt rebuild info, when, here you are in my very own back yard about to do it....Cool! & thanks for doing this...please take lots of pics.

Here's the list they sent me.

We can provide the following parts for your 12 Bolt differential:
Ring and pinion matched set part number MWGM12-411 your cost is $209.94
Master bearing installation kit part number MWR12RMK including pinion bearing, pinion seal, pinion nut,crush sleeve, carrier bearings and races, new ring gear bolts and gasket your cost is $98.00
New Eaton positraction part number MW19556-1 to replace gov lock positraction your cost is $469.99

[usmcchevy]

DavidB posted his write up in engine and drivetrain, Thanks David!

Link:
http://67-72chevytrucks.com/vboard/s...d.php?t=484897