The first one I owned, had 275K on it when I sold it and never had any fluids changed except oil. The one I have now is approaching 100K, Ditto.
Thinking back, I have never changed any fluids of transmission or rear differential on any vehicle I have owned, except when I was repairing it which were mostly leaks. Mostly put the old stuff back in and added new oil to bring to up to full. My 1952 8N tractor did have the 90 weight gear oil replaced with trans hydraulic fluid to get the rear pump working better in cold weather.
Maybe I have just been lucky.
