Posi Trac and Sure Grip • The Dodge Challenger Message Board

by **Goldenblack440** » 22 Sep 2009 11:08

I always hear these terms in relation to Chrylser (and Dana) LSD's. But what is the difference if any?

The Service manuals always seem to say Sure Grip and the "Posi -rear" is heard in discussions. Is the Posi Trac a Chrysler only thing? Or is it an entity like, say, Detroit Locker or Dana or Borg Warner that make products for various manufacturers? Anyone know for sure?

Some LSD use cones, others have springs and clutches.

thanks, steve

by **dave-r** » 22 Sep 2009 11:16

Posi is a chevy expression I think?

by **fal308** » 22 Sep 2009 12:24

Yes, Posi (PosiTrac)is a GM expression for the same thing as a Mopar Sure Grip

by **fal308** » 22 Sep 2009 12:41

Posi and Sure grip are not lockers. a locker (Detroit, Eaton, Ox,various air lockers, etc) solidly lock the axles together whereas a Posi or Sure Grip are limited slip setups. P or SG will allow an axle to go around a corner while a locker will chirp and/or hop the wheels around a corner due to them being "locked" together. Lockers are good for straightline acceleration and low traction conditions (offroad, 4x4) whereas a semi-locker is better able to live on the street.
Some of these companies are better known to the offroad 4x4 crowd as lockers are more common there than on the street.
Dana is a (bankrupt) axle http://www.dana.com/ and other parts maker as is Borg Warner (transmissions, gears and drivetrain components) http://www.borgwarner.com/
Detroit and Eaton are in the same corporation
http://www.eaton.com/EatonCom/ProductsS ... /index.htm
http://www.eaton.com/EatonCom/index.htm
Ox http://www.ox-usa.com/ox/
ARB http://www.arbusa.com/
Truetrac is an aftermarket Eaton limited slip http://www.eaton.com/EatonCom/ProductsS ... /index.htm

by **burdar** » 22 Sep 2009 13:47

Posi and Sure grip are not lockers. a locker (Detroit, Eaton, Ox,various air lockers, etc) solidly lock the axles together whereas a Posi or Sure Grip are limited slip setups. P or SG will allow an axle to go around a corner while a locker will chirp and/or hop the wheels around a corner due to them being "locked" together.

That's not really a correct statment.

A Posi and a Sure Grip are basically the same system. THey just use different parts to get the job done. THe Posi is a Chevy term and Sure Grip is a Mopar term. The older 742 Sure Grip cases used clutches and the newer 489 cases used cones to get the other wheel spinning. The posi I think just used clutches.

A locker(like was used on Ford products) only "locks" under acceleration. It does NOT lock while going around corners. A "spool" is used in drag racing to lock both wheels together all the time. That is different than a locker.

by **Eddie** » 22 Sep 2009 15:16

Burdar is correct. I really like the new Zexel-Torsen geared limited slip units! No clutches to wear out,,no cones to lose the taper and bottom out in the diff case,,all geared,,very tough! The same torque biasing"floating geared" design that the UK made Quaife diffs use in the SRT-4. :wink:

by **Goldenblack440** » 22 Sep 2009 16:24

Thanks very much guys, now i know! I didn't expect such a comprehensive understanding, but there it is. Posi is a GM term. Well i won't use that term again when talking about Mopar diffs, and now i anticipate many heated discussions from people who don't know this. That's why i never saw Posi Trac in the service manuals.

I know what fal308 means, i think Burdur misread what he was saying, he didn't say the P and SG were lockers, he just explained the difference. I did actually think the Detroit Locker did tighten up the inside wheel in turns - i know they make a heavy clicking sound when turning and i know they are not recommended for too much street use as they are hard on the axles, tyres and diff centre mechanisms (pinions shafts etc) due to this fact. And i think they actually can be adjusted a little so that they are almost fully locked or less locked. But of course they are not solid like a spool.

by **fal308** » 23 Sep 2009 8:26

You got it. :s017:

i just didn't quite explain it out enough.

by **Goldenblack440** » 23 Sep 2009 11:23

No problemo, thanks for all those links, didn't realise there were so many manufacturers or who was in bed with who. Interesting setup Eddie was talking about...the all gear LSD setup with no cones or clutches.

In Australia, Borg Warner was bought out by a company called BTR Engineering and they made some improvements for strength. These were all used in the 100's of thousands of 'bread and butter cars' such as GM products, Ford Falcons and Nissans. They are virtually identical to the old BW but now have BTR Eng. stamped on them.