I am having to replace my main clutch for the third time, although over almost a twenty year period.the last one lasted six years. all due to stripped teeth off the clutch disk

My question is if i am abusing the old girl.Maybe asking too much of her? We live in hilly forested northern ca. Dozer is used mostly for winching Redwoods out of ravines that pg&e had fallen or winching firewood logs. Occasionally skidding logs on a fire road for only a short distance. gets used maybe a dozen times a year.
I talked to General Gear,he said to look for wear on pilot(replaced last go around) and input shaft bearing wear.
Also,getting a small amount of water in the transmission. Can't come from rain as its kept in a barn. I wanted to address this while engine is out. thanks for the help.

Something simple to over look is remember to always have your clutch engaged, only disengage when needing to put it in gear. If you run the diesel with the clutch disengage for long periods of time it can start to shift/walk eventually stripping the teeth off just something simple to check and remember to do.

In regards to the water in the transmission during storage under cover. Redwoods grow and thrive in the heavy costal fog areas, in fact the leaves are designed to capture that condensation. In costal fog you have air that is at or near its maximum capacity to hold water at the given air temperature, generally with costal fog and inland tule fog the air temperature and dew point tend to track each other. Then you have all of that cast iron gets cold at night so it’s colder than the dew point during the day and you end up with condensation forming inside of the tractor. That’s why frozen clutch packs, stuck injection racks and injection pumps become quite common in tractors found in this environment / region. Things in this environment rust from the inside out, even when stored under cover. A very famous Gold Rush writer had some choice words about that areas climate when stuck in the Mendocino Redwood sawmill region, might not be what people assume the climate is based on how it is 500 miles to the south:)

Idling with the clutch disengaged is the #1 cause of stripped clutch disc teeth in D2’s and D4’s, as clayton already said. When the clutch is engaged, the disc is held securely inside the flywheel teeth but in the disengaged position it’ll rattle slightly against them, similar to backlash clicking between gears. As the clutch teeth wear, the backlash increases, as does the wear rate until the teeth are gone. If you’re already not idling with the clutch disengaged, then it’s time to check for wear inside the flywheel teeth, badly warped pressure plates that could be shifting the disc inside the flywheel, or input shaft bent/worn.

thanks for the responses. heard from someone years ago about not leaving the clutch disengaged ,thanks. I will probably need some more help when I get it apart this winter and get a good look at everything.

This is what happens to your clutch when it is not properly engaged. Ask me how I know. This picture shows the missing teeth.   

In addition to the above, I always thought wear on the pilot bearing was another major reason to engage the clutch while idling.