Posi rear end

[hdixon]

I am looking to put a posi unit into my 12 bolt 1969 step side truck what be a good unit to install if anyone can help me out on this please

['68OrangeSunshine]

I had an Auburn posi put in a 12 Bolt rear on my '67 K/10 Suburban in '96. Also had Moser axles custom cut for that build. [The GM factory was on strike at that time, so I couldn't get OEM axles.] Three years later, the 454 on the Sub had a fire and I ''downed'' the truck. In 2010, I blew out the factory Eaton Posi in the 12-Bolt rear on my '71 GMC Jimmy, so I cannibalized the differential off the suburban for the K/1500. Still on there now. Cuts tight turns.
We could not get the '71's wider rearend to fit on the '67. It's still on jacks until I can rebuild that rear.

Also, back in the '80s, I got an Eaton Posi on a 12-Bolt 3.73 rear off of a '69 GMC stepside in a junkyard. It was missing one axle so I got a new one from the Chevy dealer, and had a shop rebuild the carrier with new bearings and install it on my '68 C/10 stepside.

Both rearends are still going strong.

[Mike C]

I'm a bigger fan of the Eaton over the Auburn, but I own both. The TruTrac is an interesting choice for a street vehicle as well.

[hdixon]

do I have to change the axle to install a posi unit what is the correct size 8.875 I have seen so many posi unit till I was not sure what to buy what is a dura trac

[Jrainman]

you should not have to change axles , just make sure its a 8.875 for Gm truck application, but also as long as you are going in you might as well change all bearings and seals (rebuild)

[hdixon]

Good info I will have the bearing and seals change I get lost on the different types of posi unit I see one on ebay for 400 used but it says it is a Dura Trac I see other that say slip trac what the best one to purchase I am new at this as you can see.

[Bigdav160]

I get lost on the different types of posi unit

All types have been used by the OE's at one time or another under various names. They have their pro's and con's

Most recommended for general use is a clutch based unit. Smooth and rebuildable it is suited for street, drag racing and offroad use.

Auburn cone style. Works well but not rebuildable. Like a clutch base unit it is suitable for general use.

Gear type. Suitable for street and drag racing. Action is smooth and automatic. Can be designed with different amounts of torque bais. Very reliable. Not the best choice for off road as it can, at times, act like an open differential.

Locker type. Most abrupt engagement. Best for offroad or drag car.

[hdixon]

great good info thanks everyone for all your support with this task I have a much better idea what to look for now Merry Christmas to all

['68OrangeSunshine]

Originally Posted by hdixon

do I have to change the axle to install a posi unit what is the correct size 8.875 I have seen so many posi unit till I was not sure what to buy what is a dura trac

I only added one axle on the '68 Stepside since the donor unit was missing an axle.
On the '67 Suburban, both axles were shot. A PO had already used bearing savers once, and they were totally shot, that's why I had to get the Moser axles.
8.875 is the 1/2 ton carrier size.

[70cst]

I installed the Eaton posi in my truck ...

[Mike C]

Duratrac is a brand name. I think Yukons clutch style LSD? You don't need to change axles, but you do need to order the carrier with proper offset for your truck's gear ratio. I think on trucks it's 3.73 and higher numerically for 4 series, 3.07-3.55 for 3 series and less than 3.07 for the 2 series.

[hdixon]

is this one a good one as well


GM 12-Bolt TRUCK Posi Unit - 30 Spline - 8.875" Limited Slip - Rearend - NEW
Eaton-Style (clutch) Posi Unit - 3.73 & UP Ratios

[wfojon]

Hi,
I just had a drive line shop install an Eaton posi in my 12 bolt. The shop replaced the axles and bearings and the new posi with new bearings. The total cost was around $1500. No regrets for me.
Jon

[Mike C]

Originally Posted by hdixon

is this one a good one as well


GM 12-Bolt TRUCK Posi Unit - 30 Spline - 8.875" Limited Slip - Rearend - NEW
Eaton-Style (clutch) Posi Unit - 3.73 & UP Ratios

Is that the Duratrac? What gears are in your truck now? My 69 short step with 307/TH350 was factory 3.07

[hdixon]

this one was a little cheaper it is a Eaton slip

[Mike C]

Eaton made the original GM ones and probably has the best clutch type LSD's made today. Good to go.

['68OrangeSunshine]

Originally Posted by wfojon

Hi,
I just had a drive line shop install an Eaton posi in my 12 bolt. The shop replaced the axles and bearings and the new posi with new bearings. The total cost was around $1500. No regrets for me.
Jon

Not a bad price today, considering I spent about a Grand 20 years ago.

[hdixon]

so you thank this Eaton would be a good choice and appears to be the correct fit for my truck I don't thank nothing has every been change in the rear all factory.

[Mike C]

Unless I missed it, you haven't said what gears are in your truck. You must buy the right carrier offset for your gear ratio you have, or the one you plan to run. And the two most common gear sets, 3.07 and 3.73, use different carrier offset.

Google is your friend by the way. Google best limited slip and read for days rather than one short question at a time here.

[Ironangel]

+1 on the Eaton Posi, they were OE on our trucks and muscle cars of the 60's & 70's and still going strong today. The units available today are new and improved with stronger alloys and space age clutch materials making them in my opinion unsurpassed and worth every penny at $400. http://www.drivetrainamerica.com/195...FRCQaQodHAYICQ https://www.ringpinion.com/Technical...sitraction.inc Can you copy and paste the link for the unit you showed? Have to be careful because the $350 dollar units are Asian and are not Eaton units, "Eaton style" is not an Eaton. The unit price I posted above is the lowest price going for the Eaton 12T units. If thats the factory 12-bolt axle under that 69 it will be a series 3 carrier, (3:73, 3:42, 3:08) If we knew what gear ratio you have we can verify what series carrier you'll need. Also, do you plan on reusing your existing gears, or new gears?
And Mike is correct, your existing axles WILL work. ~Ghostrider~

[Toms67]

I am not trying to hijack the thread. Just a question. My 67 C10 has 3.73 gears in it. Can I just put the posi unit on? Without pulling the ring and pinon. And if I have to pull the ring and pinion. Can I reuse my ring and pinion?

[Mike C]

Google....

But you can remove your existing case with the ring gear, put the new ring gear on the limited slip and re-install.

The most difficult aspect of gears is setting pinion depth. This is not touched with just a case swap. You must match backlash and preload on the bearings to what is there now, but that is not hard. But entire books are written on this subject. You either need new bearings on the posi unit or pull and reuse yours. Once again, some special tools involved.

Google and read how to do this. Better yet, buy the book.

https://www.amazon.com/Chevy-Differe...al+repair+book

SO MUCH easier than when I had to figure it out in the late 80's.

[88Stanger]

Toms67
i believe you will need to remove the carrier unit from the rearend {includes removing both axles} which houses the "posi" or "non-posi" in it. Along with this is the ring gear. then you remove the ring gear from the non-posi unit and install the ring gear into the new posi unit. At that time i believe you will need to remove the pinon gear also only because you will need to reset all the tolerances, ie. backlash and such. i may be incorrect, so if i am wrong please someone chime in here.
I did mine, i had 307 non-posi. i bought an Eaton disc style posi, all new bearings and shims, then i removed all the parts from the rearend, cleaned it up and then took it to a guy who does rearends locally and for $250 he put it all back together. I did go with 3:42 gears, little more low end but still some upper end also.

[Toms67]

Thank you very much for the insight. I think I will probably have someone do it for me. Thank you.

[Bigdav160]

At that time i believe you will need to remove the pinon gear also only because you will need to reset all the tolerances

This is not true. Listen to MikeC.

No reason to mess with the pinion.