Here is an article posted about your question. I asked this question to a auto column. I don't see it worth the $ myself.
Chip: I have a Dodge 4X4 with an anti-spin differential (limited slip rear
end).
Before that I had Ford Bronco with the same.
With both vehicles I have had occasion to be off road in mud or gravel
and
had one rear wheel spin requiring me to engage 4wd to get out. I have
heard
to apply the brake to change power from one wheel to the next. This did
not
> > prove to be effective. So just what advantage am I getting off road?
> >
> > On other occasions (with both vehicles) I have spun out on ice when in
2wd.
> > Could the limited slip rear end contribute to this happening? If this is
so
> > could people who have limited slip be at risk and not know it?
Thanks again for your question. Here is an early copy of my column in
reply.
Best regards,
Chip
>
> A: According to Isaac Steele, my off-roading enthusiast co-worker,
> your problem is common: "Most hardcore off-roaders think a factory
> limited-slip differential isn't much better than a standard
> differential. Limited-slips are fine when there's not much traction
> loss, but they're almost worthless when one tire loses traction
> completely. "
>
> The differential splits the torque applied by the driveshaft and
> delivers it to the two drive axles. When the vehicle turns a corner,
> the outside wheel travels farther than the inside wheel, so the
> differential must also allow the two drive axles to turn at different
> speeds. Therein lies a conflict: how does the differential know the
> difference between a wheel that's turning a corner and one that's
> losing traction?
>
> Dozens of traction-enhancing differential designs address this
> conflict. Some, such as the Torsen differential used by Hummer and
> Audi, are factory equipment. Others are made by the aftermarket, and
> may be retrofitted to most vehicles. Each can be rated on a "torque
> bias ratio" scale of the differential's ability to transfer torque to
> the wheel with traction when one wheel slips.
>
> The standard "open differential" is at the low end of the scale. It
> has a torque bias ratio of zero -- it always transmits all the torque
> to the wheel that's slipping. Limited-slip differentials improve upon
> this. Those with clutch packs, like the one in your Dodge, transfer
> some of the torque from the slipping wheel to the one with traction.
> Those using viscous fluids or helical gear arrangements have more
> aggressive torque bias ratios.
>
> At the top of the scale, a "locker" differential will lock, or
> "spool," the two axles solidly together, so both wheels always receive
> an equal amount of torque. A spooled differential won't leave you
> stuck until both wheels completely lose traction, but it also won't
> turn a corner without scrubbing the wheels. A vehicle with a spooled
> differential can be impossible to maneuver on dry pavement, and unsafe
> to drive at speed on icy roads.
>
> In general, the greater the torque bias ratio, the greater the
> handling difficulty there will be at speed on ice. There are
> exceptions however; the Torsen differential is stable under icy
> conditions, and some locker differentials, such as the Toyota locking
> differential, or the ARB Air Locker (
ARB 4x4 Accessories Bull Bars Air Locker IPF Lights) allow the driver
> to switch between a locked and a standard differential by pressing a
> button on the dash.
>
> Factory limited-slip differentials don't generally have enough torque
> bias to create problems in icy conditions. This low torque bias is
> also why you haven't been helped by the trick of pressing the brake
> lightly when a wheel spins. The trick works well when the torque bias
> ratio is high.
>
>
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