Conversion to positraction
 

I have a 1971 Twelve (12) bolt rear end that I would like to convert to positraction. How big of a job is it and where do you suggest that I get the posi unit? Do I need any special tools? Are there any crush washers or anything like that to deal with? Thanks in advance.

Re: Conversion to positraction
 

I just had my 72 SWB converted to position. I went with a Detroit tru trac carrier and Motive 373 gears. I had a local shop do mine because you have to really know OLD 12 bolt reagents to get the spacing right. I changed everything except the rear end housing and the axles when I done mine and you will be money ahead if you do it all at the same time. All the bearings, ring and pinion and all. You can find the carriers on ebay but make sure it's a 8.875 carrier for a truck. Cars are different.

Re: Conversion to positraction
 

Yes there is a crush sleeve but you can get a kit with everything you need.

Re: Conversion to positraction
 

best to spend the thousand or so dollars drop off at shop and pick it up in a day or two

Re: Conversion to positraction
 

yup this is the easiest.

not sure how much HP you have, but several companies make a bolt-in 9" that you'd never have a problem with..but the cost is a factor of course.

Re: Conversion to positraction
 

The easiest install would be some type of lunch box locker. All you have to do is pull the axle shafts and replace the differential gears.

If you know your axle ratio and want to keep it; just order the correct posi case, a couple side bearings, and some shims (just in case) and get to work. (remember to mark your carrier caps) No reason to change pinion gear position if you're just replacing the differential case.

Re: Conversion to positraction
 

The red neck in me just screamed out ...WELD IT!.... haha jk, definately don't weld it.... seen too many of those jobs gone bad

Re: Conversion to positraction
 

I've converted to Posi on 2 trucks, over the years. First time I pulled a 12-bolt 3.73 Eaton Posi rear off a '69 GMC Stepside in a junkyard, then added a missing passenger-side axle shaft, and had a shop go thru it, with new bearings and checking condition and mounted on my '68 C/10 Stepside. Still going good.
Second time, when old axle bearings [PO's 'Bearing Savers'] failed on a '67 K/10 Suburban, I got new axle shafts from Moser, an Auburn Posi and a rear-end bearing install kit and took the parts to a local shop to assemble and install on the Sub. Worked good until the engine [454] had a fire and I sidelined the Sub. In 2010, the 12-Bolt 3.73 Eaton Posi in my '71 Jimmy blew up, and I cannibalized the whole '67 rear and mounted it on the '71 GMC. Going good once again.
Eaton Posi units are rebuildable. I hear Auburn Posi-s are not. Both operate well.

Re: Conversion to positraction
 

Thank you all!!!!

Re: Conversion to positraction
 

I was wondering. For someone like me who is mechanically challenged, have a mechanic do it, so start saving.

Re: Conversion to positraction
 

...what is really funny tho'....is the person who made the 'Epic Fail' advert.....spelling surprised incorrectly ('suprised'...lol)....epic fail for sure.

C.

Re: Conversion to positraction
 

...what is really funny tho'....is the person who made the 'Epic Fail' advert.....spelling surprised incorrectly...lol....epic fail for sure.

C.

Re: Conversion to positraction
 

I bought a 12 bolt Posi traction rear end out of a 1964 C10. Before you start scouring the bone yards looking for one of these rear ends, let me fill you in on the specifics of this particular rear end:

This rear end was made by "Dana" for GM, it's pretty rare to start with, the only other car known to use this posi traction carrier was the '64 corvette, and it uses 17 spline axles. besides the fact that I had to get the axle flange stud holes plug welded, and the flanges re-drilled for a 5" x 5" bolt pattern, these axles are known to be weak. Most people will tell you to go the route of installing an Eaton Posi carrier, mostly because the parts are very plentiful.
Once I started calling around looking for rebuild parts for this rear end, most shops, Including Randy's ring and Pinion all told me the same thing, no parts exist to rebuild these. I beg to differ though. As I mentioned, the '64 Corvette shared this particular posi carrier, and you can buy the clutch packs for these through Corvette restoration companies, albeit expensive though. that being said, I decided to replace all the bearings and seals and set this unit up stock, since I have no intention of doing drag strip launches (with the exception of a few burnouts here and there :lol:) This unit should last a long time.
I can tell you this though, even though I didn't rebuild the carrier, this thing is tight......
When I brought the chassis home with the cab mounted on it, I attempted to back it into the driveway, the whole ass end kept sliding sideways, as if no spider gears, wouldn't give an inch, had to put a jack under the rear in order to turn it enough to get it in the driveway!
Here are a few pictures of the unit before I rebuilt it... and after. Notice the absence of the panhard bar attaching stud.....I had to cut the ugly bracket off the axle tube, which was there for the '64 C10 bar, and since I was lowering the truck, I just made my own track bar out of steel tubing and rod end bearings that are L/H and R/H thread, like a turn buckle, so they can be adjusted, and welded a bracket to the lower right hand trailering arm to attach the bar to, and I retained the factory upper bar mount, and last but not least, the rear end bolted in just like the factory original did, same track width, same trailing arm mounts.
Ben
:metal:

Re: Conversion to positraction
 

two more pictures...
Ben
:metal:

Re: Conversion to positraction
 

I fell into mine ,I bought a '67 parts truck with a bed and cab full of extra parts and it came with a 3.73 posi a 292 and a bone straight short bed frame and delivered on a flatbed for $500.00 the 67 running driving truck with fog lights has one too and I paid $1,100 for that truck , Some days it's good to be a Grumpy old man :metal:


http://http://i957.photobucket.com/albums/a...psupfckpph.jpg

Re: Conversion to positraction
 

"The red neck in me just screamed out ...WELD IT!.... "

That's the first thing that popped into my head! I miss the good old days....

Re: Conversion to positraction
 

I've converted several...with the right tools it's not that hard.

If it costs $1000 for a posi install, I need to quit my engineering job and start doing these.

This one is the Auburn ECTED electric locker that's in my Blazer.

http://i235.photobucket.com/albums/e...psc2211382.jpg

Putting a new Eaton Posi in my K-10
http://i235.photobucket.com/albums/e...psnv5fkkp3.jpg

Re: Conversion to positraction
 

There's an auburn for sale here(NOT MINE) he wants $350.00 -$400.00 with bearings

Re: Conversion to positraction
 

I got my install gratis because I was having it rebuilt at the time, and it didn't cost any extra to install the locker (TrueTrac, actually, the helical locker kind). My bearing races were spinning in the assembly, so it had to be machined. Good thing I took it apart I guess!

Are these the same as the car 12-bolt where you shim them left and right in order to get the backlash right? I've done the dial indicator (and depth mic) but never set up a truck one.

Do you need to do the contact paint also? I've done all three (dial, depth, contact) hoping to catch any error I might make, but never had much luck with the contact paint. Maybe it's a special paint?

Re: Conversion to positraction
 

Yes, they are the same as a car 12 bolt as far as setup goes. Shims to set backlash and preload, and paint for pinion depth / contact pattern.

Re: Conversion to positraction
 

So did I. The 1969 longbed frame I bought to use has a 12-bolt 3.73 posi-traction rear end in it. I lucked into that one.

Gary

Re: Conversion to positraction
 

I think they're referring to parts and labor.

Typically it's around $150-250 labor to "set up" a ring & pinion and carrier. A good LSD or Locker will cost around $350-500 depending on brand and intended usage. A set of gears(if needed) cost about $200-250. A rebuild kit with all the gaskets, seals, crush sleeve etc. is usually around $100.

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Yeah...i know. I was joking. ;)

Re: Conversion to positraction
 

Grumpy,
That's a calendar shot right there!
Oh yeah, about positraction rear ends, I plan to try a Eaton Detroit Trutrac gear type. Low maintenance and smooth operation I am told.
Russ