I’m currently working on a Yanmar ZT350 drive that stopped shifting reliably due to contaminated oil. Shifting is by means of two multi plate clutch packs, actuated by a piston located between the two, fed by a pair of solenoid valves. In other words, it’s pretty much like any other hydraulically shifted transmission of comparable power level.
The failure mode is several sintered metal pucks from the clutch pack breaking apart, whereupon the material has been ground to a very fine powder by the gear train, rendering the oil a deeply lustrous shade of metallic green. The fine metal particles have subsequently lodged themselves in the very tight clearances, bringing things to a halt.
I have been warned by several highly competent engineers with much equipment specific experience against having anything to do with this. Apparently, once things have gotten to this stage, the drive tends to never get reliable again, because it is practically impossible to fully get rid of the contamination. The Yanmar ZT drives have rapidly lost the workboat market because of this exact fault. However, the powers that be want me to forge ahead, so here I go.
My plan is to make things as clean as possible with chlorocarbon solvent, compressed air, lots of clean oil and a paint brush. I then intend to flush the drive several times with DFO once it’s on the boat. Any thoughts? Does someone know of a magic pill for this type of situation?