10 fastlane
techtorque
HOW TO CORRECTLY
MEASURE A REAR END
FOR CUSTOM AXLES.
Story and Photos by Wayne Scraba
Adding big power to your car comes
with consequences. Hardware that
normally doesn’t flinch is suddenly
hard pressed to keep up. Add big,
sticky tires to the equation and you
just know what will happen next:
carnage.
Among those pieces that regularly seem to be
taxed are the rear axles. It’s always wise to upgrade
to stronger axle shafts whenever possible, even if
it’s just for your own peace of mind. But if your car
has a narrowed rear end or if you’ve swapped in a
rear end from another car, it’s tough for the tech
guys at Summit Racing to figure out what the axle
dimensions should be.
Complicating things is that there all sorts of
different axle spline combinations for spools
and limited slip applications. It’s easy enough to
make an error here but more times than not, it’s
a case of simply not being on the same page as a
given manufacturer when measuring the housing.
Something else that crops up is pinion offset. Some
cars have a rear end that has an offset pinion gear.
When an axle housing is setup with pinion offset,
each axle shaft is a slightly different length.
But fear not. We can show you exactly how to
measure a rear housing for custom axles. It’s all
very straightforward; once the dimensions are
established, there’s no need to worry about axles
being too long or too short. Here’s how to do it.
FINDING AXLE
HOUSING DIMENSIONS
Here is a list of axle housing dimensions you’ll need to
make. Make sure to double-check your measurements as
you won’t be able to return custom-made axle shafts.
• Housing width flange to flange
• Driver side housing width, flange to pinion center
• Passenger side housing width, flange to pinion center
TYPE OF REAR BRAKES
You’ll also need to tell the axle manufacturer what type of
brakes you’re using in the car. On our example setup, we
have a standard small GM backing plate and a conventional
9.5 inch small car (Nova, Camaro, Chevelle) steel brake
drum. These drums typically measure 3.200 inches wide to
the outside of the axle register. Most axle manufacturers
also require a brake drum thickness measurement; take a
reading at the axle register.
Take a look at the photos as we measure a Strange
Engineering S60 housing for axles.