AIR BRAKES -- GENERAL INFORMATION
Figure 17 - Mainifoled Tractor Protection Valve
DIFFERENTIAL POWER DIVIDER LOCK VALVE
Air can be used to engage or disengage the power
divider lock used on tandem drive rear axles. Three
conditions are presented to clarify the identification of the
power divider locks.
Condition 1
Prior to the FMVSS 121 regulation, the air operated
power
divider
lock
(PDL)
had
air
pressure
for
engagement
(lock)
and-spring
pressure
for
disengagement (released). The air source could be at
any convenient location.
Condition 2
When FMVSS 121 split brake system was introduced,
some tandem axles were equipped with power divider
locks which were disengaged (released) with air
pressure and spring controlled in lock or engaged mode.
Plumbing of the spring brakes and power divider lock in
this condition eliminated spring brake units at the rear
axle. When the spring brakes are applied, air is expelled
from the power divider lock allowing the spring pressure
to lock up the differential and assist the spring brakes.
Figure 18 - 4x2 Tractor With Initial Spilt Air System With Modular Control Valve
For Spring Brake and Tractor Protection Control
CTS-4154Y - Page 16
