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.

['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 ...

[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

[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.

[Ironangel]

Originally Posted by 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.

Like Mike indicated, since Toms67 is using his existing gears he wont have to mess with removing the pinion, only the carrier. The hardest part of that aspect is removing the bearings from the old carrier and pressing them back on the posi unit. That requires a bearing splitter, a puller, and a press. Heres a list, https://www.amazon.com/dp/B01F62S2RO?psc=1
https://www.amazon.com/OTC-927-Ton-P...EDSPRH2HB78JZ1
https://www.amazon.com/Goplus%C2%AE-...ydraulic+press

[Toms67]

Well that's good news. Thank you so much for the help. The people on the forums are super. So much information. Love it.

[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.

[Accelo]

Yes, you don't have to mess with the pinion.

I wouldn't recommend a carrier change without replacing the pinion bearings and seal, unless they were recently replaced. You can't remove the carrier bearings without damaging them. So to save the time and frustration most just install all new bearings on the new carrier. So why not purchase all the bearings / seal and do them at the same time? Excellent time to make any pinion adjustment for preload and depth.
So now you have the equivalent of a new differential with used gears.
perfect in my book.
Rick

An old thread!

[Ronald29609]

I just had an Eaton posi installed in my 12 bolt 67 truck differential. $650 for parts and $350 labor so $1000 +/- total. The 3.73 gears were good so we reused them.
BTW Tom of Tom's differentials passed away. Business is for sale.

[BCOWANWHEELS]

new eaton 395.00 do it yourself. no big deal

[Mudflat]

395.00 from where?

[Romo912]

Originally Posted by 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

I didn’t know how to start a thread
Posted via Mobile Device

['68OrangeSunshine]

Originally Posted by Romo912

I didn’t know how to start a thread
Posted via Mobile Device

Go to a forum topics list like ''The 1967-1972 Chevrolet & GMC Pickups Mesage Board''

Upper left, below 2 headers and above ''Announcements'' is a capsule:
[NEW THREAD]
Push that and go. Make sure you make no typos, since it can't be edited, once posted.
But I don't know if this works from a mobile device.

[71longbed-brew]

I went with Eaton
Changed the ratio from 3.08 to 3.42