final drive oil: interval, what oil, and the plug trick

book on most machines that size says check at 500, change at 1,000 or 2,000 depending on the year. i change at 1,000 on every machine i am responsible for and i check every 250 by cracking the plug. it is a 10 minute job and a gallon of oil. a final drive on a 313 is 6 to 9 grand rebuilt, more if the housing is scored.

the plug trick, since you put it in the title: park with one plug at 12 o'clock and one at 3 or 9. the level plug at 3 tells you the level, the top one is fill. crack the level plug, if oil runs out clean you are good, if it is grey or smells burnt you are not. if nothing runs out you have been running it low and you have a different problem. takes longer to walk to the machine than to check it.

oil: the manufacturer spec is a GL-5 gear oil. cat sells theirs, an 80w90 GL-5 from a real brand meets the same spec. i have run both, the drives do not know the difference. do not run a hydraulic oil in there because "it is all oil," i have seen that.

what a failing one looks like before it fails, from the one i lost on a 2012 Deere 210G: a wet ring of mud stuck to the sprocket hub that would not dry, then a slow track when tramming that i blamed on the ground for two weeks, then a rumble at low speed you could feel in the seat. by the time you feel the rumble the bearings are done. the wet ring was the tell and i walked past it every morning. that drive was 11,400 with labor.

on yours tom, milkshake with no rumble means you caught it. floating seal (the duo cone seal) is probably what let the water in. drain, flush, refill, run a day, drain again, look at what comes out. if the second drain is clean you may get away with a seal job instead of a rebuild.

adding one for the big machines. on a 40 ton class the final drives hold 3 to 4 gallons a side and the plugs are big, use the right size socket not a pipe wrench, the plugs strip and then you are drilling. and when you refill, the oil is slow going in through the top hole, use a pump not a funnel or you will be standing there for half an hour in the wind.