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| Illustration 1 | g01125065 |
The parking brakes are applied by springs and hydraulically released. These wet brakes are engaged through the compression of a series of disks and plates. The disks are splined to the output shaft. The plates are splined to the brake housing. The flushing system directs oil through the brake housing in order to cool the internal components. The flushing system also cleans the internal components.
Charge pressure is used to release the parking brakes. When the brakes are engaged, the passage for charge pressure in the brake housing is open to the hydraulic tank. The brake springs move the brake piston against the disks and plates. This action compresses the disks and plates, so the output shaft cannot rotate.
When the brakes are released, charge pressure is directed into the piston cavity. Charge pressure acts against the brake piston against the force of the brake springs. The charge pressure overcomes the spring force, and the brake piston moves. This movement releases the compressive force on the disks and plates.