Quantcast Figure 6-14.Automotive type emergency/parking brake axle mounted.

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Figure 6-14.—Automotive type emergency/parking brake axle mounted. are  usually  mounted  on  the  output  shaft  of  the transmission or transfer case directly in the drive line. Theoretically, this type of system is preferred for heavy equipment  because  the  braking  force  is  multiplied through the drive line by the final drive ratio and the braking  action  is  equalized  perfectly  through  the differential. Drawbacks are that severe strain is placed on the power transmission system, and also that the vehicle  may  move  while  it  is  being  lifted  since  the differential is not locked out. Parking brakes interconnected with service brakes are usually found on automotive types of equipment (fig. 6-14). This type of emergency/parking brake is actuated by a foot pedal or a dash mounted handle assembly  and  is  connected  through  linkage  to  an equalizer lever (fig. 6-15), rod assembly, and cables connected  to  the  emergency/parking  brake  mechanism within the drums/discs (fig. 6-14) at the rear wheels. When you test parking brakes, stop the vehicle on a road graded at about 30 percent. Set the parking brake and  release  the  service  brakes.  The  vehicle  should maintain its position and not roll or inch backwards. Repeat the test in the opposite direction. Again, the vehicle should hold its position. If there is no hill close by, you may test parking brakes by setting the brake, placing  the  vehicle  in  first  gear  (low),  and  slowly releasing the clutch with the engine idling (do not rev the engine while doing this exercise). This action should stall the engine of the vehicle you are testing. In the case of an automatic transmission, the vehicle should not move in any gear. In either of these tests, if the vehicle does move, it is an indication that there is a parking brake malfunction. Once you determine there is a problem, proceed as follows. First, inspect the condition of the emergency brake linings and contact surfaces just as you would for service brakes and just as carefully. Pay attention to the ratchet and paw] or any other automatic locking device that holds the brake in the applied position to make sure it is operating properly. In addition, when inspecting the drive line type brake, examine the universal joints and splines for loose bolts and grease leaks. Loose bolts are not  uncommon  for  vehicles  having  brakes  mounted  in the drive line. The emergency brake must hold the vehicle on any grade. This requirement covers both passenger and commercial motor vehicles equipped with either the enclosed type of emergency brake at each rear wheel or a single emergency brake mounted on the drive line. The Figure 6-15.—Equalizer linkage. 6-18



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