what do we have?
03-22-2004, 05:33 PM
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what do we have? WS.6's and SS's have what....Limited slip....posi...or what else stock? im not very informed bout this kinda stuff..thanks for the help
03-23-2004, 06:23 PM
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Positraction is GM's brand name for their "limited slip"
rear. Like Traction-Lock is for Ford and Sure-Grip
for Chrysler.
There are few, or maybe no truly limited slip rear ends.
A limited slip rear would enforce a maximum relative
rotation speed and allow free differentiation below it.
It would be great, if you could buy one that acted
that way.
The clutch-type "posis" have the wheels held together
by friction. They don't differentiate at zero load, there
has to be an applied torque differential to cause
differentiation and a high torque differential can't be
held. This is almost the opposite of what we really want
but since it works, it's used.With one wheel in the air
you still get all the torque the clutches can hold, to the
other. I've seen some chunks that had ramps to add
further clamping pressure above the base spring load,
under harder use. Seen others that were just flat stacks
of plates. But a clutch is a clutch, more or less, only some
can be rebuilt and some you get to throw out.
The Zexel Torsen in the stock F-Body operates
differently. It allows free unloaded differentiation.
There is some kind of internal gizmo that senses the
applied torques and instantaneously biases input torque
to the more-loaded wheel. This is better than an open
diff where the loose wheel gets all the torque. But, it
can only bias up to about 2:1 (3:1 on the T-2R) so the
loaded wheel only gets 2X the slipping wheel torque.
2 x 0 = 0, which can kinda suck. But on dry pavement
it is a good differential. Just where you need a good
differential, yeah. T-2R along with higher split adds
a preload which acts as if there were some baseline
torque to bias.
The closest thing to real limited slip is probably the viscous
coupling differential. These just don't take big power. One
day they will probably have MR fluid diffs that are all smart
and everything and a true limited slip will arrive.
Torsen is better for road racing because it makes no scrub
and no heat in the turns; it differentiates freely. A "posi"
is scrubbing every time you turn and power turns (and
burnouts) are what wear the clutches. Too much heat in
the clutches can mess stuff up. In a design that augments
clamping under load there can be a safety problem; you are
raising the clamping and still trying to differentiate. "Back in
the day" word used to be that the GM 12-bolt ruled at the
strip but would blow up on the circle tracks, where the 10-bolt
was the reverse. Take that bit o' folklore how you like.
rear. Like Traction-Lock is for Ford and Sure-Grip
for Chrysler.
There are few, or maybe no truly limited slip rear ends.
A limited slip rear would enforce a maximum relative
rotation speed and allow free differentiation below it.
It would be great, if you could buy one that acted
that way.
The clutch-type "posis" have the wheels held together
by friction. They don't differentiate at zero load, there
has to be an applied torque differential to cause
differentiation and a high torque differential can't be
held. This is almost the opposite of what we really want
but since it works, it's used.With one wheel in the air
you still get all the torque the clutches can hold, to the
other. I've seen some chunks that had ramps to add
further clamping pressure above the base spring load,
under harder use. Seen others that were just flat stacks
of plates. But a clutch is a clutch, more or less, only some
can be rebuilt and some you get to throw out.
The Zexel Torsen in the stock F-Body operates
differently. It allows free unloaded differentiation.
There is some kind of internal gizmo that senses the
applied torques and instantaneously biases input torque
to the more-loaded wheel. This is better than an open
diff where the loose wheel gets all the torque. But, it
can only bias up to about 2:1 (3:1 on the T-2R) so the
loaded wheel only gets 2X the slipping wheel torque.
2 x 0 = 0, which can kinda suck. But on dry pavement
it is a good differential. Just where you need a good
differential, yeah. T-2R along with higher split adds
a preload which acts as if there were some baseline
torque to bias.
The closest thing to real limited slip is probably the viscous
coupling differential. These just don't take big power. One
day they will probably have MR fluid diffs that are all smart
and everything and a true limited slip will arrive.
Torsen is better for road racing because it makes no scrub
and no heat in the turns; it differentiates freely. A "posi"
is scrubbing every time you turn and power turns (and
burnouts) are what wear the clutches. Too much heat in
the clutches can mess stuff up. In a design that augments
clamping under load there can be a safety problem; you are
raising the clamping and still trying to differentiate. "Back in
the day" word used to be that the GM 12-bolt ruled at the
strip but would blow up on the circle tracks, where the 10-bolt
was the reverse. Take that bit o' folklore how you like.
Last edited by jimmyblue; 03-23-2004 at 06:29 PM.
