MOTOR TRUCK SERVICE MANUAL
Fig. 1 Internal Spring Design Differential Locking Unit (Exploded View
The differential locking unit consists of several parts, all
assembled around the spider.
The No SPIN differential (Figs. 1 and 2) provides equal
Spider and Center Cam Assembly
amounts of drive line torque to each rear driving wheel
and also permits differential action for turning corners.
This assembly consists of the spider, center cam and
spider snap ring.
The spider has four trunnions
This differential also provides greater operating flexibility
projecting radially from a center ring on each side of
than a conventional differential, because the locking type
which are located fixed driving clutch teeth. These teeth
differential overcomes wheel spinning when required to
vary in number, depending on the size and model of
operate in mud, sand, snow and on ice or wet roads.
differential. The internal diameter of the spider is
The unit is installed in the differential case in place of the
uniform. Into it is mounted the center cam. This cam is
conventional gears, pinion and spider.
held in position with a centrally mounted snap ring which
permits the center cam to be rotated within the spider but
The action of the unit is the same for both drive and
prevents lateral movement.
The center cam is
coast loads and forward and reverse driving.
symmetric, having the same number of cam lifts on each
side as there are clutch teeth on the spider. These lifts
or "icams" have uniform contours with rounded surfaces
that provide anti-friction ramps for disengaging the driven
Two types of No SPIN differentials have been used on IH
vehicles; they are (a) Internal Spring Design, Fig. 1 and
(b) External Spring Design, Fig. 2.
Driven Clutch Members
The difference in the two units is explained in the text;
Two identical driven clutch members are located on
however, the disassembly will cover the internal design
either side of the spider and center cam assembly. Each
has a set of clutch teeth
Fig. 2 External Spring Design Differential Locking Unit (Exploded View)