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positraction, Detroit Lockers, etc.

1829 Views 6 Replies 2 Participants Last post by  Art
My 67 Fastback is equipped with a positraction rear end. I wasn't really aware of this until towing it home and noticing the obvious 'click, click, click' of it around turns (and no, it's not a broken open-end :) - I became most happy when I heard it!

Is positraction the same thing as detroit locker? Neither are the correct term for such ratcheted rear ends on mustang correct?

I seem to recall hearing that positraction mustangs had their exhaust exit in front of the rear axle. While I have never believed this to be true, my car does indeed have its exhaust exit in front of the axle. As the original exhaust hangers are doing just that - hanging unused, I suspect that my car had an original "normal" exhaust.

Can somebody shed some light this? Was what I heard about posi and exhaust totally bunk? Are there any instanced where this was the case?

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· Registered
6,777 Posts
Never heard that about the exhaust, but I can't imagine it's true. It's the Detroit locker that clicks going around corners.

Discussion Starter · #3 ·
If you could, post the data tag that should be attached to one of the nuts on the pumpkin. I've never seen an 8" with a factory locker. Do you have a 9" rearend?

No '67's had the exhaust exit anyhwhere but behind the axle. A PO did that. They may have added a locker as well.


[color:blue]'68 Coupe
250/C4, 221 Argentine Head
Breakaway Converter, 9", 3.50's/T-lock</font color=blue>

· Registered
7,478 Posts
"Positraction" is actually a term that G.M. used for their positive traction carriers. "Equa-Loc" and "Trac-Loc" are the names Ford used on their positive traction carriers. The only early Fords I know of where the exhaust exited in front of the rear wheels was a 65 Shelby and a few 66's. A Detroit Locker will "click" going around corners, so will a Trac-Loc that needs some friction modifier added.

An easy way to determine which one you have is by jacking up the rear, turn the back tires in one direction, then jerk the tire in the opposite direction.... A Detriot Locker will disengage at that sudden direction change and spin freely... You will hear the click, click, click.

A Trac-Loc will not dis-engage, but will slip when the torque will overcome the pressure on the springs/clutches inside the carrier.... The book says 90 ft/lbs. With the car in gear (or in park) and the rearend off the floor, with some effort, you can make the carrier slip

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Discussion Starter · #5 ·
Just on the subject of terminology, Posi-Traction is a marketing term made up by GM for their version of a limited-slip differential. Ford used the name Traction-Loc. From what I understand both systems are similar in that they use a clutch pack to bias torque. A Detroit Locker uses dog clutch engagement, it's much more abrupt but it's capable of a true, positive locking of both wheels. Detroit Locker is a brand name used by Tractech.

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