posi swap

[bigmac73]

I am trying to find a Posi 12 bolt unit to rebuild and install in my 72 C-10,

will a car 12 bolt internals fit in a truck housing? and what years and models should i be looking for. I can rebuild a old one not trying to spend a lot of cash on a used assembly

[RustyBucket]

I think the car 12 bolt is different internally. Factory posi truck rear ends aren't plentiful or cheap.... not 'round here anyway. I'm about to spend the money for an Eaton posi carrier and gear set for my BLAZER.

[68c10airstream]

Hi Guys, if you really want to do the rear end repair correctly and have it last you should use a tool called a "case spreader". It works like this, set the backlash and pinion depth with slight drag on the side bearings. Basically not sloppy side to side, and also not pressed (forced in). When you are happy with the results you add .004 thousands to the shim thickness to both side (carrier) bearings. Now spread the case and instill the now wider shims. Release the case spreader and you now have bearing preload (longevity). You would have to pry the ring gear to get it out. I watched alot of guys in the garages i worked in hammer thicker shim stock in and bend them, break the cast iron factory ones, etc, etc. The case spreader is on ebay, a little expensive but isn't the rear end worth it. Bearings are not cheap these days for quality ones. I mention this because i can't remember the last time i've seen somebody mention it . I too broke and bent some until i went to school and went by the gm factory instructions. I would borrow the factory tool from the local dealer and the typical comment would be " what do you need that for, nobody here uses it" Good luck, Brian F. P.s. it bothers me that in todays internet access it isn't mentioned more. I know I'm old school.

[LONGHAIR]

It is simply not necessary. The only time you need a case spreader is with those big Dana60 housings. I would be more concerned about cracking a smaller axle by trying to spread something that doesn't need it.
I have done hundreds of 10, 12, and 14 bolt axles as well as Dana25, 27, 30, 44 and Fords.....it'a D60 thing.

[joesgreen67]

Isn't a 12 bolt car posi 28 spline vs. truck posi 31 spline?

[RustyBucket]

I think the after market carrier part number is different between the truck and car.
This thread kinda reminds me of the guy that asked the time and learned all about how a watch is made or repaired. .. my wife's a little like that sometimes

[68c10airstream]

Boy it didn't take long to be put in my place. I felt the rearend advice was appropriate, lengthy yes. I wish somebody would have told me about the case spreader years ago when i took the advise of an OLDER mechanic. No doubt it was my responsibility as i could have read the manual. Well, enough is enough.