Posi unit recommendation for 12bolt
 

Hi guys, I have a 69 c10 with 3.73 (i6) and starting to plan a removal and overhaul.

While I’m in there I’d like to upgrade to a posi unit.

Wondering what the popular ticket is these days? Eaton? Other?

I’m looking for something that will be comfortable on the street but strong /durable.

Thank you

Re: Posi unit recommendation for 12bolt
 

About the Mid-Ninties I had the 12-Bolt 3.73 rear end go out on my '67 K/10 Suburban. It had a 454/TH350/NP205/3.73 drivetrain. Bearings went out after unknown mileage. A PO had already used Bearing Savers.
I had the whole carrier rebuilt. Moser axles, since I couldn't get OEM 6-lugs bc the plant had a strike going with the UAW. I went with an Auburn Posi. I spent around a thousand 30 years ago. The Sub had an engine fire [ '98] and a big insurance company totalled it for me and I got a Salvage Title. So it sat. In 2010, the stock Eaton posi on my K/1500 GMC Jimmy, broke, trying to pull a deadbeat's Scouts off my property.
We cannibalized the whole rear end off the '67 Suburban and bolted it on the '71 Jimmy.
I know the widths differ between the years. Somehow, we got the skinnier '67 carrier under the '71 chassis. Putting the '71's carrier under the '67 chassis didn't work. It's still on jacks.
But the point is I've had real good luck with my Auburn. It's run on two trucks. You can't rebuild them, they say. Eatons are good too, and rebuildable. But I haven't had to rebuild an Auburn.

Re: Posi unit recommendation for 12bolt
 

I did an Eaton TrueTrac a few months ago - pleased with it so far.

Re: Posi unit recommendation for 12bolt
 

I'm very happy with my TrueTrac. I forget it's there until it's needed and then it does its thing without any problem.

Re: Posi unit recommendation for 12bolt
 

Another vote for the TrueTrac, it's probably the most street friendly unit. No need for friction modifiers like the clutch type. I have them in two of my trucks.

Re: Posi unit recommendation for 12bolt
 

Go Eaton, not Auburn.

If you are switching to higher gear ratio, you will need a different carrier size than the 3:73 IIRC

Re: Posi unit recommendation for 12bolt
 

Anything made by Eaton is good. Auburn's are okayish but they are not rebuildable like an Eaton.

Gary

Re: Posi unit recommendation for 12bolt
 

That's one of the beautiful things about the Truetrac. There's nothing to wear out so there's nothing to rebuild.

Re: Posi unit recommendation for 12bolt
 

Brian also votes for Eaton True-trac helical locker.

This has no clutches to wear out and does not require limited slip additive. Just use regular old 75w90 gear oil.

Another cool thing is that unlike a traditional locker, you don't have to worry about getting off the throttle before entering a corner. The true-trac acts like an open differential until there is a rotational difference between the wheels.

A bad thing about this design is that it will not lockup if one wheel is completely without traction. For example, if one wheel is in a low mud hole, it will just spin. The fix is to lightly apply some drag to the spinning wheel (use the brake pedal) and it will lock right up.

Anyway, this is the best you can get for a daily driver. If you are off-road or really trucking, get a Detroit Locker. These are bullet proof and deliver 100% torque to both axles. They do require some thought about how you drive or you can have a really bad day. If you approach a corner nearing the limits of your handling, as soon as you left off the gas in the apex, the locker unlocks and this throws the dynamics of the chassis off. Can cause you to lose control.

Re: Posi unit recommendation for 12bolt
 

I'm a Tru Trac guy. Upgraded to the 30 spline unit as needed depending on the vehicle and 30 spline axles from Moser.
Also the Tru Trac doesn't need any posi additive.

Re: Posi unit recommendation for 12bolt
 

My 1969 12-bolt has had an Aurburn cone-type diff for >20 years. Had a chirping problem when driving fast around corners, even though I used the Auburn friction modifier additive. Solved the problem when I replaced a leaky gasket, and used Lucas gear lube that didn't require an additive.

It's worked like a champ since then. Of course the truck's mileage is probably no more than 1K-2K per year, so I doubt I'll ever have to replace it. That, plus I suspect the hardened steel cones will last a lot longer than fiber clutches. Back then I think I paid around $400 for the Auburn and installed it myself. Couldn't believe how nice the OE ring and pinion looked after almost 200K miles.

Re: Posi unit recommendation for 12bolt
 

My 72 C20 has a 511cid big block with 700 lbs ft torque. I installed a Detroit locker by Yukon, and it works great. I was afraid the 511 made too much torque for anything but a spool. The locker works great, not one issue and it works great on the street no matter the weather.

A friend of mine put an Eaton True Trac in his 67 step side that has a blown 383. The Tru Trac is working perfectly and he loves it, very street friendly.
We both had differential issues because of what we have. And we both burned or broke several different brands of posi units before we settled on these.

Live and learn!!

Re: Posi unit recommendation for 12bolt
 

I have Eaton Tru-Tracs in my 72 C10 and my 92 K1500 4 x 4 Suburban. As has been said install em and forget about them and you don't you have em till u need em. After the install on my 72 C10 I noticed when I take corners/curves maybe faster than I should I can feel the inside tire gripping the road as the Tru-Trac is doing its job.

Re: Posi unit recommendation for 12bolt
 

Eaton Tru Track it is, thank you all for the input!

also, is there a different P/N depending on what your gear ratio is?

Can anyone link me to the right one for my 3.73 equipped 12 bolt?

Also, any installation tips would be appreciated, thanks all

Re: Posi unit recommendation for 12bolt
 

Go on Eaton's website and its easy to find your right one.

Re: Posi unit recommendation for 12bolt
 

Good choice. I don't think you can go wrong with any of them for street and occasional dirt road driving.

Re: Posi unit recommendation for 12bolt
 

What was with the 71 not fitting under the 67???

Re: Posi unit recommendation for 12bolt
 

The carriers are of different widths. The earlier unit is about 1.5~ - 2'' narrower than the later unit. We were able to bolt the narrower unit on the Jimmy. But we would have had to stretch the springs' width to get it on the Suburban. Since it is not a runner [Salvage Title] we did not try too hard.
Possibly with a long enough farm jack we could have made it fit.