[65gto69]

Hi guys, question on 12 bolt rear. How much work does it involve to convert an open rear to a posi rear? Does it just involve putting in a posi carrier and gears or is there more involved. I can get an open 12 bolt for next to nothing, and I have seen 12 bolt carriers on ebay for 200-300 dollars. Thanks for the input and help.

You Have To Be Willing To Take It To The Max!

[65gto69]

Hi guys, question on 12 bolt rear. How much work does it involve to convert an open rear to a posi rear? Does it just involve putting in a posi carrier and gears or is there more involved. I can get an open 12 bolt for next to nothing, and I have seen 12 bolt carriers on ebay for 200-300 dollars. Thanks for the input and help.

You Have To Be Willing To Take It To The Max!

[GTO]

Just take out the open carrier and bolt in the Posi, tighten up your backlash if needed and drop the hammer! ... Eric.

[GTO]

PS. There are 3 different carriers so make sure you get the one for your gears. ...Eric.

[68CONV400]

Or you could get a Powertrax unit and not have to drop the carrier at all...

http://www.powertrax.com/



Hope this helps,

Charlie

[Never Enough Power]

65gto69, If you do pull the carrier don't forget to check the inner bearings and outer bearings on the axle shafts. I usually change them just to have piece of mind. I installed an Auburn posi unit in my latest project, very nice unit , not cheap but if buy cheap... you usually get cheap!

[Dave Schiffers]

What kind of power or 1/4 time will the PowerTrax "LIVE" behind ?

['ol Pinion head]

If the gear ratio is what you want, one can install a posi after ck'ing current backlash in several spots. Object is to recreate current backlash with the posi carrier, no reason to blow $400+ on the clunky Powertrax-units.


Let's use the example of .009 backlash, just re-shim to get close to .009, even .008 or .011 should be fine on a driver. Say the current backlash is loose from worn gears or loose pinion, say .024 or .028 backlash...really sloppy , sucking the backlash back in to .008-.010 is not a good thing, as is, as gears have reestablished a pattern at that loose a backlash. Reinstalling pinion gear with new crushsleeve & setting backlash to .008-.010 will usually create a noise problem. Better to remove pinion bearing & add 1/1000th pinion shim, before bringing backlash in to say .012.

When installing new Eaton carrier or rebuilt !2 bolt Eaton carrier, consider the old side shims are not going to work. I draw from big stock of used side shims to pick a correct side shim for lh cap side, then use GM service spacer & correct thin shim on the right side. Without having a large selection of used side shims & a $100 selection of new GM thin shims, some times just easier for one time posi installer, to buy a set of Raytech shims or the wild interlocking shim stacks. either that or buy the GM Service spacer & mooch a side shim & ccorrect cast spacer off local r/e pro.

[68CONV400]

In reply to "Grumpybear":

Takes 6,000 to 36,000 ft-lbs of torque. Much stronger than the axles

Zytanium construction is 67% stronger than titanium

No wearing surfaces. No friction clutch packs to burn out


Hope this helps,

Charlie

[68CONV400]

Eaton carrier-$399.95
Ring and pinion installation kit-$19.99
(Pinion depth setting tool and dial inicator-if you have them)$0.00


Total-$419.94 (add around $100-150 for tools if needed)



Powertrax-$299.95
Rear end cover gasket-$9.95


Total-$309.90




Charlie

[68CONV400]

PS- all prices were from Summit for a GM 8.875 in. ring gear 12 bolt.

Hope this helps,

Charlie

[P455]

On the other hand, here's some pictures of the PowerTrax No-Slip unit that fragged in my rear after only about 20 miles of break-in use!

PowerTrax Photos

This was behind a mild 455 on rain-dampened streets after a slight wheelspin.

I hope this isn't indicative of the quality of the unit. I hope this was just a defective one. It was installed correctly and passed all tolerance and operation checks upon installation.

They're sending me another one. I have my fingers crossed.

[insert witty signature here]

[68CONV400]

20 miles of break-in while spinning the wheels?

Ring and pinion gears take 500 miles to break-in.

Charlie

['ol Pinion head]

Comparing prices...

From new Summit 35th Anniversary catalogue:

$19.95 "install" kit includes no side carrier shims. To get Raytech kit with side carrier shims one pays $41.95. As an alternative for flexible shim stacks, to buy two bags of interlocking 12bolt type shims from O'Reilly's: $54.00. Traditionally use GM shim selections .056-.060 12 bolt are disco'ed, thus need for some Raytech pieces...

Only GM Powertrax units in my Summit catalogue are No-Slip units $419.95-429.95 each.

Having over 80 lbs of 12 bolt cast side shims organized by size, typically bill out one GM side shim & one GM service spacer (under $8.00 together) on any 12 bolt gear set/up or posi build.

One new 400# preload 3 series 12 bolt Eaton posi carrier off e-Bay delivered to my doorstep $315.00

$315 + $8= $323

To just install a posi, no reason to use my over $700 in pinion depth tools... just a small brass hammer, & a $50 magnetic base dial indicator, which also use for many other automotive functions (good investment).

[P455]

Charlie:

"slight" wheelspin, as in anytime you attempt to take off from a stop sign with a 455 and BFG T/A tires on wet pavement... Engine revs never got above 2,500. Oh, and Powertrax says a 50 mile break-in is recommended, but not required for proper operation.

[insert witty signature here]

[goatseeker]

P455,
Your photos are precisely the reason why I decided not to go with the PowerTrax and put in an Auburn Pro instead.

http://kurtspontiac.homestead.com/TimSimpson66GTO.html

[Skip Fix]

Tom's Differentials has some decent prices. His Eaton 10 bolts are cheaper than Summit's.

[68CONV400]

P455

My apologies for implying the damage was caused by driver error.And you were also correct about the 50 Mile break-in (even for my Richmond ring and pinion gears(checked the left over installation instructions last night)).

The Powertrax unit is what I've been considering on buying for quite a while now.Without having much previous input from others who have tried it,I may have been trying to sell myself on the concept more than acually being very helpful to this post.

Again,my apologies.

Charlie

[P455]

No problems, Charlie.

I want to make it clear I'm not bad-mouthing the PowerTrax unit, and that I hope my experience was "one of those things" that happens. I intend on installing the replacement unit and fully breaking it in gently before passing judgement on it. I realize defective products make it out the door sometimes.

[insert witty signature here]

[Half-Inch Stud]

I don;t like the Power-Trax concept for our level of GTO Street car luxury.

Rather leae the P-Trax for gravel-haulin trucks.

"tbdET/1xxMPH/1.xx 60foot/28"/3.54:1/10"/469 #48/Flat HYD/DualQ-Jets/Offyl/3xx0Lbs
11.00/123MPH/1.50 60foot/29.5"/4.10:1/10"/469 #48/FlatHYD/DualQuad/Wenzler/3250Lbs
12.00/112MPH/1.61 60foot/26"/3.31:1/10"/469 #48/FlatHYD/Q-Jet/Torker/3650Lbs
12.70/103MPH/1.71 60foot/28"/4.10:1/12"/469 #48/FlatHYD/Q-Jet/Torker/3950Lbs"