All our drive shaft failures occurred in the same month & year and root cause for that failure was operators changing direction at high idle with full loads (axle are the weak link in that chain). Defiantly operator ("on-purpose") damage. As far as F/R hyd fluid MCFA, NACCO, LINDE, Taylor all use the fluid if requested. Out of the four manufactures LINDE and Taylor offer foundry packages the other piece together a custom type foundry truck. Molten metal will stick almost anything except chrome rods, it may melt around the rod and cause wiper or rod seal damage and leakage but not damage to chrome. You can fabricate covers that if secured on one side will lay on top the tilt cylinders and rods to prevent molten metal from contacting this area. Parker offers an F/R type hyd hose that holds up very well dont remember the # but comes in a blue skin color. I believe Right Line offers a fork positioner/side shift package that has a front plate guard that will keep the molten metal away also. Polycarb protection only last a couple weeks after its cleaned a few times it becomes dangerous because you cannot see through. I like the high heat impact resistance glass been using this for the last three years for windshields without issues works very well. bottom skid plates can help if operators drive through molten metal (I have had them do that and burn one to the ground) helps prevent splash into the engine/transmission areas. Usually dont have an issue with molten metal on the lift cylinders because they are behind the mast uprights out the splash path. Best advice I can give is while cycling through your current fleet recommend manufactures that have specific OEM foundry packages, in the meantime improvise, invent, find new ways to load furnaces, retrain operators how to properly load a furnace etc