Dual range tandem drive axles, Description and operation – Spicer Drive Axles Application Guidelines User Manual
Page 85
AXAG-0200 June 2009 85
Description and Operation
Two-Speed, single or
, are dual range
shiftable axles. They provide low and high range
gearing and are designed for heavy-duty service in
on-off highway operations. Low range for deep gear
reduction and slow speed hauling off highway. High
range for cruising speeds on on-highway.
The complete tandem axle assembly includes two
axle units, each with double gear reduction
capability coupled by a 2-gear power divider.
Dual Range Gearing
The gearing for each axle is a combina-
tion of a spiral bevel ring gear and pin-
ion and a planetary unit.
First reduction (High Range) is pro-
vided by the spiral bevel gearing.
Second reduction (Low Range) is
through the planetary gearing. Four
planetary idler pinions are confined
within the ring gear internal teeth. The
planetary gears rotate around a sliding
clutch gear.
Each axle is equipped with a shift unit,
which operates the sliding clutch gear to
provide a means for selecting the axle
range. Range selection is accomplished
through the movement of the sliding
clutch gear in and out of engagement
with low and high-speed clutch plates.
Gearing and Torque Distribution - Dual Range Gearing
The sliding clutch gear is locked
into the high-speed clutch plate and
rotates as part of the differential
assembly. The planetary pinions are
stationary and the axle uses only the
pinion. Power flow is through the
drive pinion, ring gear, differential
unit and
The sliding clutch gear is shifted
into engagement with the low-
speed clutch plate (an integral part
of the bearing adjuster). The
sliding clutch is held stationary
and the planetary pinions are
forced to rotate around it. Power
flow is now through drive pinion,
ring gear, planetary gearing,
differential unit and
The axle uses two reductions to
multiply torque. The planetary
unit adds approximately 36%
more reduction to the primary gear
set. Torque is multiplied on an