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I have a new Eaton series 4 carrier that I want to install in my 12 bolt with a new set of gears.

I have never done this before but really want to learn.

How bad is it? Anyone know of a good book that might help me?

I am a drum to drum type guy Doug.. maybe Flyin' or pro70 will help

I put aftermarket gears in a 12 bolt once back in my youth. As I recall it wasn't all that difficult, just time consuming. Keep adjustin' shims 'til you get a nice pattern on the gears, that's about all I remember. Bought the 9" for the "Z" from Danny Miller already set-up...... I cheated.

yep.. Danny for gears...

you'll need a dial indicator to set backlash. your gear set should come with a sheet showing the pattern you want, the hardest part is getting the carrier bearings preloaded right ( the factory has a spreader, that's what the holes on either side of your diff are for) it's not too hard, just takes patience.

Thanks man, I think i'll see if I can find some directions on installing it before I start. Then I'll go at it.

I have the new diff.
By the way Toms differentials.GREAT guy to deal with. The Eaton that I got from him for $350 was something like 425 through summit.

I still have to get the gears and an install kit.

I have a dial indicator and base.
Wort case is that I can't get it and have to take it somewhere.

Thanks for the help.

this is what is so cool about this place and pro 60's site... real world answers to real questions.. no hype, no lies, no BS....

Seems to me that you need a 4 series case to install 4 sumpthin gears on 12 bolts.

aren't a 4 series and a series 4 the same?^^^^ see 1st post^^^

Seems to me that you need a 4 series case to install 4 sumpthin gears on 12 bolts.

It's not the case, it's the carrier. I did buy a series 4 carrier.

I have also learned the difference is in the width of the ring gear.
You can buy a 4.10 for a series 3 carrier from richmond it's a 4.10 "thin"

There may be more to it than that but..... I dunno..

I know that I didn't do my homework all that well because i thought (there are always problems when I do that) I could get a 3.90 gear for this carrier and I can't. At least not an American made one that I know of from Richmond or US Gear.

That's ok though, I will use the 4.10 and a 28" tire instead of a 26" tire and still trap about 6300 rpm with the new motor.
Then I can save my pennies for 4 speed automatic that's beefy enough for me.