Re: Determining Traction Aiding Devices in Diffs

[jlandry@domain.elided (John A. Landry)]

On Fri, 05 Dec 1997 11:57:28 -0500, tsm1@domain.elided (Tom Mandera) wrote:

>Wow, John.  Nearly everything you posted seems counter to my train of thought..

Oh well... that's why I'm here... to learn something.

>As I recall, most "permanent" (not ARB / Command Locker / whatever) lockers
>allow one wheel to OVERRUN the driveshaft, but never turn SLOWER than the
>'shaft.  Thus, you *should* be able to turn one wheel while the other is on
>the ground, since the driveshaft won't turn, and thus the tire on the ground
>doesn't have to turn, and the tire in the air can turn (though you may hear
>the locker unlocking (think a typical ratchet mechanism, sliding "backwards"
>on the ratchet results in clicks)

This sounds logical to me, however, let's take something like the
Lock-Rite... I thought it takes quite a bit of torque to make the thing
unlock (and overrun the slower tire).  The amount of torque (I would think)
it would take would not be something you'd easily do by hand simply by
trying to turn the raised wheel.  Contrast that with an open differential
which can be turned with your pinky.  The difference should be easy to
feel.  Thus, if it can be turned freely = no locker, etc., etc.

>I would turn this around, and try turning the DRIVESHAFT with one wheel on
>the ground.. if the 'shaft won't turn, good shot you have a locker (BUT,
>could an Open diff be "stuck" or have "picked" the axle shaft on the ground
>at this particular point in time?  making the same result?).

I guess the driveshaft test would be a good one also, but who wants to
crawl under *there* and get all greasy? <grin>

>My undertanding on the limited slip units:
>
>The Track-lok allows slipping all the time, but *limits* the slip.  Thus, it
>acts exactly like an open differential, until the "difference" between one
>wheel and the other becomes too great, thus the term "ramping up" the LS.
>As the rotational difference increases, the clutch packs "ramp up' and bind
>together, causing the fast wheel to slow, or the slow wheel to speed up,
>resulting in the two axle shafts being fully locked together.  I believe
>this situation persists until you get off the throttle and allow the
>clutches to "unbind" themselves.
>
>I've heard the older PowerLock works differently, in that it's locked ALL
>the time, UNLESS it's forced to unlock.. this is much more like a
>"traditional" locker

I could be wrong as usual, but I think you've described them perfectly
backwards... but then I can never keep the damn names straight!

>Again, Detroit/Lockrite's drive the slower of your two wheels, thus the
>oversteer in corners (inside wheel tries to PUSH the truck wide in the turn)

Yes

>So, how would I check for a LS or Locker?

Pull the cover of the carrier and LOOK at it!  <grin>

>Jack the axle up.. BOTH sides.  Turn the driveshaft.  If one wheel turns,
>you don't have a locker (both wheels will turn the same speed with a
>locker.. the same speed (x gear ratio) as the driveshaft, if one is
>stationary, no locker)

[very scientific testing procedures snipped]

>YMMV, I may be wrong and John right.. the FAQ has some info (I think) on
>figuring out if you have an Open, LS, or Locked diff.

Never!

Happy holidays,

John
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