opinions on posi brands?

[RapidRide2]

I am going to be rebuilding my 83' gmc rear diff. soon. I am going to switch from a 2.56 to a 3.73 posi. What are your opinions on factory gm,, auburn,, eaton,,, and richmond powertrax. This truck will be street driven with about 300 h.p. I want good street manners fronm the posi yet reliable and strength. I only want to do this once. p.s. has anyone ever retrieved a rearend from a junkyard with good success????? Thanks in advance. Matt

[Captkaos]

Factory GM used Eatons and for yours it used the Gov-Loc. Auburns I don't care for because they are cone type and when they wear, the destroy themselves and are not rebuildable. I heard they were changing them, but.... I am using Eatons LSD on mine, it is what came factory in the 12bolts.

[7T7]

Have you looked at the DETROIT TRUE-TRAC?
After looking at all the different limited slip differentials on the market, this looked like the best.
No clutches that burn out, easy to install (if you weren’t changing gears) and good street manners.

Tractech

[DennyB]

The auburn i sold was a clutch and spring type. I didn't know auburn made a cone type.
But as Chris states you may want to steer clear of the cone type as they are not rebuildable.
I have seen these (cone type) fail at the track too. So durablity is also an issue.

[Captkaos]

Originally Posted by DennyB

The auburn i sold was a clutch and spring type. I didn't know auburn made a cone type.
But as Chris states you may want to steer clear of the cone type as they are not rebuildable.
I have seen these (cone type) fail at the track too. So durablity is also an issue.

Denny, I wanted to verify my info before I commented, but Auburn does have a clutch/spring type, but the clutch is the cone clutch, so all of them are cone types for the Limited Slip's
http://www.auburngear.com/aftermarke...differentials/

The ended up not changing the design apparently, but are offering a D-REX program that replaces the case and all other componenets: http://www.auburngear.com/aftermarket/drex/

[DennyB]

Chris, Thanks for the clarification. I thought the auburn had a clutch and friction disc setup.
It’s good of them to provide the D-REX program.
The only problem I see with that is the D-REX program is only good for 4 years. After that, what’s the cost?

I also want to clear up one more thing. The units I have seen break at the track are powertrax No-Slip units.
They seem fine for street use but a high HP engine with sticky tires seems to be a bit much for them.
But then again, I don’t think this application is what there designed for.

Thanks again for the correction Chris.

Denny

[DennyB]

7T7, The TRUE-TRAC you provided a link to is very intresting.
Do you know any one that has used it?

[7T7]

We put one in a 69 camaro about a year ago and have had no problems with it. The guy hits about 12 autocross races a year.
We were looking for something that could handle big horsepower and still be good for autocross.
The Truetrac was definitely the ticket!
I like the way it worked in the 69 so much, I put one in my current 77 project truck. (which still is in the works)
The cheapest place I found to purchase a Truetrac was "4 Wheel Parts". $415

[TIMSPEED]

I desperately wanted the TrueTrac, but they don't make it for a Series3 12-Bolt, only Series4...so I went with the Eaton Posi, and it's been great so far.

[DennyB]

I'm moving this to the Engine & Drivetrain board with a redirect. I will also stick it to the top for a while so it does not fall off the page and you can find it.
It will get better exposure there for additional answers to your questions.
Plus that is where it belongs

[Primed67]

I'm running an Auborn Pro Series chunk. It has been in the truck for 6 years now and took a lickin. I busted a set of Richmond gears but the Aurborn chunk is still in great shape and working just like it was designed.

[72k5]

Eaton makes 2 versions of their posi. One is a HD unit with more (22 vs. 14) clutch plates and stronger preload springs. The HD unit has much better grip, but is more likely to chatter and chirp the tires in turns. I believe the Moroso unit (Eaton rebadge) is the HD unit only, but you might want to confirm that if you order one. The standard version is what you got as an option from GM, unless you are getting a Corvette (not to be confused with the GovLock that GM also provided as an option in past and current years - the GovLock is a whole different animal).

The HD version never failed me, traction wise, even rockcrawling. I have a feeling that the std. version might have, it I had given it the chance, but it was much calmer on the street.

Point is - make sure you get the version you want if you order an Eaton. BTW - You can put a HD clutch and spring kit in a Std. housing if you want to upgrade your OE Eaton.

I can confirm that it is possible to break the spiders in these, but I think they are as strong as anything else in that size diff.

[boraxman]

I did the 12 bolt in my truck w/ new Eaton posi & 3.42 gears, new axles, seals bearings, labor, brakes for about $1300....works great

[shadetree]

Good thread. I'm saving my money for an Eaton posi, and 3.42 ring and pinion, can anyone advise if setting up a 12 bolt ring and pinion is as difficult as it looks?

[72k5]

Originally Posted by shadetree

can anyone advise if setting up a 12 bolt ring and pinion is as difficult as it looks?

Well, define difficult... If you have a puller for the carrier bearings, a press and associated items to remove and install the pinion bearing, and plenty of shims to choose from, no, it's not too difficult. Lacking one of the special items above could make for a real PITA job. Like so many of the things we do, having the right tools makes all the difference.

[shadetree]

I have no press, but I do have everything else. I do have a good machine shop available, though, that has a press. Setting up a ring and pinion is about the only thing I haven't done in my many years of wrenching.

[72k5]

Well, if you have everything else, with a little luck, you might be able to get the pinion shims right on the first shot, so only one trip to the machine shop. Be forewarned that you will probably need to pull and reinstall the carrier bearings a number of times to get everything right. That takes just the right two jaw puller, and a small impact gun, or it can be miserable.

One thing many people miss is that they pattern the gears without a load on them. You need to somehow provide resistance, so that you have to turn the pinion firmly with a wrench when patterning. Unless you do, the pattern will be meaningless.

If you can do it so that you are not in a hurry to get it done, I say get a good set of instructions and go for it. Setting up diffs is probably one of my favorite things to do. If you want to do one and really enjoy it, do a 14 bolt. They have the threaded collars and you can just dial the adjustment in. Sweeet!

The first diff you do will take 4X as long as the 4th one you do. Have fun.

[shadetree]

Thanks for that responce. I'm going to hone out an inner pinion bearing, to get the depth right, being able to slip the honed out bearing on and off. Then have a new bearing pressed on when I'm ready. Thanks for the info on loading the gears, I'd never have thought of that. Good solid info, thanks