the Ford 8-inch Differential
Powertrax Lockright Installation
recently have Ford vehicles come standard with some sort of
traction device in the differential. Although traction-loks
and Detroit Lockers were optional in the 60's and '70's, fact
is majority of cars simply came with an open "peg-leg"
differential. This was hardly adequate in keeping the wheels
from spinning with the factory power levels, let alone the asphalt
melting torque most of our engines are churning out these days.
We recently looked into getting some traction for our 8"
equipped 1967 Mustang. If you don't already know, the 8"
rearend is pretty much the stepbrother to the 9". Although
it is very similar in design, and is fairly strong, it has been
overlooked in the sense that there just aren't many cost effective
options for upgrading an open 8" rearend. In fact the 8"
has long been considered a "weak" rearend, yet what
most people don't realize is that in stock form, most of the
internals (spider gears, side gears, bearings) are the same
pieces as the 9". In fact, not only will an 8" rearend
hold up just fine behind the stoutest of 289 and 302's, it will
save 100 lbs over a 9".
Anyway enough history... Powertrax Corporation has developed
the Lockright differential not only for the 8", but the
8.8" and 9" Fords as well.The beauty of the Lockright
is that it is a locking differential, which means in straight-line
acceleration the axles are positively locked together and the
wheels turns at the same rate. When turning the unit un-locks
and differentiates torque to each wheel, so that the inside
wheel turns slower than the wheel on the outside of the turn.
Unlike a posi or traction lock differential, which operates
on clutches which eventually wear out and slip, a locking differential
provides a true mechanical lock-up of the two axles.
Since we were going to go through a complete rebuild of the
tired 8" rear end, we opted to install a new set of 4.11 gears.
Since we'll be installing a new ring and pinion we let West
Coast Differentials in Sacramento, Ca handle the assembly.
However you can install the Lockright in your garage in about
half-a-day, so long as you are not changing the ring or pinion
settings. The unit comes with detailed instructions which walk
you through the installation.
Our old and tired carrier (a.k.a third-member or pumpkin)
is disassembled. Be sure to mark the bearing caps so you
can identify which side they go back on, they have a wear
pattern and thus are not interchangeable.
Once the bearing caps are removed the differential case
can be lifted out of the carrier, and the ring-gear unbolted..
The differential is like a clamshell, Eric uses thin chisel
to split the two halves.
Here are the guts of the stock open differential; two side
gears, one spider gear (the other one is in the other half
of the shell) and the single cross shaft. The Lockright
requires use of a hardened cross shaft. Test the stock shaft
with a file; if it scratches or groves the shaft, replace
it with a hardened piece..
A press must be used to remove the pinion from the pinion
housing, and also to remove the pinion bearing.
The hard parts were cleaned in a solvent tank. Nothing like
In this picture the side gear is placed on the Lockright
supplied driver. It is critical that the height measure
a minimum of 1.165 inch (not including the thrust washer.)
Any less and the unit will not function properly. Ours did
measure slightly less, so WCD replaced the worn side gears
with new ones.
On the left is a new side gear, with no wear on the teeth.
On the right is the old gear with considerable wear. If
you can't tell the difference from the photo, don't worry,
the Lockright instructions come with detailed diagrams.
Reassembly of the case; place a thrust washer in the case,
followed by a side gear, then the Lockright driver, and
then the pinion shaft block...which is what you see in the
larger half of the case in this picture.
T he hardened pinion shaft is driven in between the two
short shafts which come with the kit.
A closer view of the pinion shaft block with the long shaft
between the two short shafts. Note the four holes in the
driver; this is where the tiny springs and pins supplied
with the kit go. Don't forget these or you'll have to pull
it all apart again!