What shaft in a power shift transmission has the
reverse drive gear keyed to the front of the shaft?
What components are the heart of a hydrostatic
What component in a hydrostatic drive system
maintains system pressure by using oil from the
A hydrostatic drive pump with a movable swash
plate is known as what type of pump?
TRACK AND TRACK FRAMES
Learning Objective: Identify the operational
components of the track and track frame. Describe the
maintenance procedures used on tracks and track frame
The undercarriage of crawler-mounted equipment
c o n t a i n s t w o m a j o r c o m p o n e n t s T R A C K
ASSEMBLY and TRACK FRAME. This under-
carriage (fig. 6-18) is provided on equipment that must
have positive traction to operate efficiently.
The track assembly consists of a continuous chain
surrounding the track frame and drive sprocket. The
links of the chain provide a flat surface for the track
rollers to pass over, as they support the equipment.
Track shoes are bolted to the outside links of the chain
and distribute the weight of the equipment over a large
Figure 6-19 shows a cutaway view of a section of
track chain, showing the internal arrangement of the
pins and bushings. As the tractor operates, the drive
5. TRACK BUSHING
2. MASTER PIN
7. TRACK PIN
4. MASTER BUSHING
Figure 6-19.Track chain cutaway.
sprocket teeth contact the track pin bushings and
propel the tractor along the track assembly.
The pins and bushings wear much faster than other
parts of the track because of their constant pivoting, as
the track rotates around the track frame. This pivoting
results in internal wear of both the pin and the bushing.
As the pins and bushings wear, the track lengthens.
When it does, the track is adjusted to remove excessive
Bushings that show lots of wear on the outside are
good indicators of inner wear that is also nearing the
maximum allowed by the manufacturer, if the track is
to be rebuilt. To determine whether the track should be
removed for rebuilding or replacement, measure the
outside of the bushings and track "pitch" (length of the
Figure 6-18.Side view of crawler tractor chassis.