Gradall 534C-10 (2460-4129) Service Manual - Manual (Page 58)

Reason for Park Brake Check
Park brake wear can cause park brake failure and reduce braking effectiveness on a slope.
With the park brake engaged, start the engine. Position the 2WD/4WD switch for two-wheel drive. With the
rear wheels aligned straight ahead, move the shift lever to the forward position and run the engine full throttle
(2500 RPM-2700 RPM). If the brakes are working properly, the machine will not drive through the brakes.
High backpressure in the actuation line can affect the brake holding power. To determine whether the brake is at
fault, remove the brake actuation line and plug. Check the park brake operation again. If the machine does not
move, the brake is working properly.
Backpressure should be less than 20 PSI with oil at operating temperature. To check this pressure, tee a low
pressure gauge (1,000 PSI), hose and adapter in the brake actuation line. If it is higher, check for proper operation
of the park brake solenoid valve. Disconnect the brake actuation line and tank return line at the valve and plug
them. There should be no oil flowing from the open port on the park brake solenoid valve. The brake actuation
line should not be kinked. There should be no restriction back to the reservoir.
See Figure 8C.
FIGURE 8
PARK BRAKE SOLENOID VALVE
There is a 10% wear factor on the 8 original rotor discs in the extended park brake assembly (P/N 9114-4160).
Thus, the 2 “thick” discs (0.150") each have a minimum allowable thickness of 0.135". The 6 “thin” discs (0.062")
each have a minimum allowable thickness of 0.056".
To remove park brake assembly, remove 4 drive motor nuts and slide motor out of the way. Take snap ring off
and remove coupler. This will allow access to pinion nut. Take pinion nut off and remove park brake assembly.
Park Brake Assembly Rotor Discs
Original Thickness No. of Discs 10% Allowable Wear Thickness
0.150" 2 0.135"
0.062" 6 0.056"
Spring free length is one inch. Anything less reduces brake holding power. Any combination of the above
circumstances reduces brake holding capability.
See Figure 8, Figure 8A, Figure 8B and Figure 8C.
Also refer to “Page 6-6” in the Parts Manual (P/N 2460-4100) for breakdown of park brake assembly.
IV. Park Brake
Form No. 29633 3/97
6