Re: Another Engine Swap Question

[n9ads@domain.elided (Howard R Pletcher)]

On Thu, 24 Dec 1998 22:36:08 -0700 (MST) Tom Mandera <tsm1@domain.elided>
writes:
>On Fri, 25 Dec 1998, Daniel Nees wrote:
>
>>    The 800B wouldn't need axles changed at all. The 'Power-Lok' is an
>> excellent limited-slip traction device. I have one in my 71 and love
it.
>> It is a geared limited slip as opposed to the Trac-lok that was in the
>> Scout II's, there are a clutch plate limited slip and thus wearout
>> easily.
>
>Shame on you, Dan!
>
>The Power-Lok uses clutches JUST LIKE the Track-lok.  They are BOTH
prone 
>to wearing out.  However, the PowerLok *IS* the better of the two for 
>off-roaders.. it's a more positive setup, and can be re-setup (triple 
>belleville or was that double?) to be even "tighter" and provide even 
>MORE positive traction.
>
>The only *geared* Limited Slip I'm aware of is the True Trac from 
>Dynatrac (Detroit).. and it wasn't an OE offering in the Scout 
>anything.
>
>;-)
>
>BTW, can someone provide me with some *real* details on why a Tracklok
is 
>so much "weaker"?  My input to a discussion on the "nw4x4" list was
kinda 
>tossed aside by someone because I'm still running my "weak" Trashloc and

>how could I know what I'm talking about.. or some such.
>
>I've heard the Tracklok is a 'weak' diff.. and not a great LS either.. 
>but is it *weaker* than.. Open?  *WHY*?  And how much weaker?
>I'm not concerned about the LS clutches wearing out and acting like an 
>open diff.. that's fine.  But... ker-blooey concerns me. :-)
>OTOH, $500 for a shiny new Detroit could be 
>$500-almost-afford-that-winch-I-want.
>
>
Both diffs use Belleville springs to apply pressure on the clutch packs
mounted between the diff case and the axle side gears.  The difference
between the two is that in the Power-Lok. the cross pins for the bevel
gears between the side gears are mounted in a V-shaped ramp rather than
being tightly fit in a round hole as in an open diff.  The torque applied
to the diff causes the pins to ride up the ramps, increasing the load on
the clutch packs (but it doesn't actually lock them in any way).  The
cross pins are not joined in the middle so that one pair of bevel gears
applies force to one side, the other set applies force to the other side.
 When turning, one side will ride down the ramp of the V and allow for
easier diff action.  (It's not easy to visualize without good pictures,
or a working model, but this is how the service manual explains it.)

In the Track-Lok, the cross pin is rigidly mounted to the diff case like
the open diff, so the only LS action comes from the clutch preload.  The
service manual says the following about testing a Track-Lok:

"No precise methods of measuring limited slip diff performance are
generally available in the field.  A functioning unit can be determined
by these relatively simple vehilce operational tests.

"1.  Place one wheel on good, dry pavement and the other on ice, muc,
grease, etc.
"2.  Gradually open throttle to obtain maximum traction prior to
"break-away." The ability to move the vehicle effectively will
demonstrate proper performance."

A demonstration I heard was being used in the showrooms was to put a
piece of Kraft wrapping paper under one wheel on a tile floor and a 2x4
in front of a front wheel.  If the vehicle would drive over the 2x4
without spinning the paper out, the Track-Loc was functioning properly.

In addition to the amount to limited-slip action, a difference between
the two was that the Power-Lok used 2 cross shafts and 4 bevel gears,
while the Track-Lok had only one cross shaft and 2 bevel gears, the same
as the open diffs.  Whether this difference is enough to make the
Track-Lok go ker-blooey more often, I've never heard.  It probably
shouldn't be any different than the open diff.  I understand there's been
a Track-Lok on the ultimate endurance test in Montana for some time and
it hasn't broken yet.  :-)

I not heard of anyone who has done it, but ti would seem that the clutch
packs of the Track-Lok could be shimmed to provide greater locking action
as is done with a Power-Lok.  Possibly that's because if they're tearing
it down anyway, they just installed a another diff rather than playing
with the Track-Lok.

On the original engine swap question, I would add a caution about how
hard you plan to run the truck.  The front axle is a Dana 30 which was
used with the V-345 up until 1974, but if you're planning on building a
stadium racer or something, it's probably not up to the job.

Howard Pletcher
Howteron Products Scout Parts

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