After an initial diagnosis by a previous fitter, we were assigned the job of the final drive replacement and to diagnose the extent of the system contamination and carry out necessary repairs.

The obvious failure


Enough material from the final drive had entered the return filter to open the bypass valve and enter the main hydraulic tank and begin filling the suction screen. evidence of foreign material was found in the pump suction pipe. decision made to remove tank for cleaning along with the pump. Pump was disassemble and found to be in good condition despite some evidence of contamination entry. resealed pump with a new drive coupling.

Whilst cleaning the pipes and hoses it was noted that the majority of the contamination was transferred through the case drain circuit, the swing box however shared the same case drain piping, on removal of the “tee” piece, some material was evident in the in the swing box case drain port, further examination required and with due cause, large amounts of material had entered into the swing box all the way down to the bottom bearing, creating a time bomb if it wasn’t addressed. Swing box was then removed, cleaned and reassembled.

After fitting tank, pump, swing box and new final drive, tank was filled with oil and pumps were bled. started the machine and allowed oil to flow through circuits. all circuits were then bled. After rechecking the circuits for contamination, more material was found and after a discussion with the client, the machine was to be moved from the creek bed it failed in, and transported back to the work shop, The original intention, but its location and failed state meant for an expensive retrieval.

Once arriving at our shop, we quickly removed, disassembled and inspected one boom cylinder and the bucket cylinder. The bucket cylinder was clear of contamination, but had a damaged rod and rod seal. The boom cylinder however had evidence of contamination. Another discussion with the client and all cylinders were to be removed, cleaned and resealed.