986K Large Wheel Loader Systems Caterpillar

Illustration 1	g00830985
Location of the Components for the Parking Brake (1) Piston. (2) Disc. (3) Plate. (4) Chamber. (5) Bolt. (6) Hub. (7) Shaft. (8) Plate. (9) Bolt. (10) Bearing cage. (11) Bolt. (12) Spring. (13) Plate.

The parking brake is positioned on the rear of the output transfer gear case. The parking brake is a multiple disc brake with a dry cavity which is engaged by springs (12).

Plates (3) react against four bolts (11). Bolts (11) are anchored into bearing cage (10). Discs (2) have splines on the inside diameter which engage with hub (6). The hub is splined to shaft (7). The shaft is driven by one of the transfer gears. The discs turn with the transfer gear shaft.

Illustration 2	g06268541
Parking brake switch

The parking brake switch is positioned on the left side of the dashboard. This switch operates the parking brake control valve.

When the parking brake control switch is in the on position, oil flows from the accumulators to chamber (4) behind piston (1). Piston (1), plate (8), and bolts (9) are pushed to the left when the oil fills chamber (4). Shaft (7) is able to rotate when the pressure on plates (3) and on discs (2) is released.

When the parking brake control switch is in the off position , the flow of oil from the accumulator stops. The flow of oil to the parking brake also stops. Oil in chamber (4) drains back to the hydraulic oil tank. Springs (12) then exert force on plate (13). Discs (2) and plates (3) are clamped together. This compression of discs (2) and plates (3) engage the parking brake.

When the pressure in the accumulators decreases below 6035 ± 515 kPa (875 ± 75 psi), the parking brake engages. The position of the control knob indicates the status of the parking brake.

Drive-Through Mode

The drive-through mode allows the operator to move the machine in a failure of the hydraulic system. Approximately 15845 kPa (2300 psi) of oil pressure is supplied to the parking brake during normal operation. This prevents the springs inside the parking brake from engaging the parking brake. If there is a hydraulic failure and pressure oil is not available, the parking brake will engage. First speed forward, first speed reverse, second speed forward, or second speed reverse must be used in order to drive through a parking brake that functions correctly.

First, shift the transmission speed selector lever to first speed forward, first speed reverse, second speed forward, or second speed reverse. The machine ECM will show that a warning and the transmission will not engage.

Next, shift the transmission speed selector lever to the NEUTRAL position.

Finally, shift the transmission speed selector lever back into the first speed position that was originally selected. The ECM will now allow the transmission to engage.