58 MARCH 2020 scca.com
Last month in this column, we covered what a differential does and how the
various types of limited slip differentials
function. This month, we’ll cover some pros
and cons of each type of differential, which
vehicles come with LSDs from the factory,
and how to choose the right one for your
car, surface conditions, and driving style.
An important part of choosing the
correct differential setup has to do with
your vehicle. An MR2 or Boxster has a
mechanical advantage in traction thanks to
engine placement. A Mustang or Camaro,
however, do not. Consequently, consider
this a warning that your mileage may
vary. Your driving style and the surface
you intend to run on will also influence
your decision – if the surface is mostly
hard pack, you may want a unit with less
lock on acceleration or deceleration.
Conversely, if you’re dealing with ice, snow,
or mud, a differential with a higher lock
percentage may be the best selection.
The cheapest differential is always the
one that’s already in the car. As such, there
are several ways you can snag a car for
RallyCross that’s already equipped with an
LSD. Some examples of popular RallyCross
vehicles that were available with factory LSDs
are some models of the venerable Mazda
Miata, the B13 and B15 generations of the
Nissan Sentra SE-R (Spec V version only for
the B15 chassis cars), and, of course, the
STI versions of the Subaru Impreza. Some
hidden gems with factory LSDs include the
Mazdaspeed Protegé, the Mini Cooper S
(optional on 2005-’09 model years), the
Chevrolet Cobalt SS, the Saturn Ion Red Line
twins (optional on both), the 2004 and later
Toyota MR2 Spyder, and certain E36 BMWs.
Some vehicles even came with different
types of LSDs within the same generation.
For example, the early 1.6L Miatas equipped
with LSDs came with a viscous unit, while
the later 1.8L cars received a Torsen. Many
will tell you that the Torsen is the superior
unit, but some prefer the earlier viscous
unit and it’s buttery-smooth operation.
WHAT’S THE DIFF?
PART 2: Without the right limited slip differential in your RallyCross car, you may find yourself
spinning your wheels. But which diff is right for you? | WORDS Matt Wolfe | IMAGES Dave Green