You may think this is goofy , but if kept out of the elements , these tractors are kind of like army tanks . There are '40s vintage Sherman tanks in South/Central America that have been kept clean & repainted & look brand new . The armored hulls , turrets etc. don't "wear out" . The mechanical wear parts have to be replaced when worn . I think at this point they are having trouble finding replacement mechanical parts for them .
However , we aren't pushing around 30 tons with antiquated , strained engines/transmissions , and from what I've seen , these tractors could last a VERY long time , IF properly maintained & operated .
On the gear drives , there are 3 main mechanical components that can suffer abuse/neglect .
1 . The engine . With regular tune-ups AND oil changes , it is not out of the question to get 2500 hrs out of a K-Series Kohler . I would honestly , conservatively guess my '74 112 is used only 50 hours a year . But it's 40 YEARS OLD ! That's 2000 hrs ! Original short block ! I change the oil once a year & usually burn 1/2 a quart in between .
2 . The transaxle . From what I understand , by FAR the most common reason for failure is attempting to shift gears while moving & the secondary pulley is still spinning , ie: grinding the gears . My brother & I did that , along with nephews & nieces , & it is going to need an overhaul sometime soon..........also , AFTER 40 YEARS !
3 . The variator . My Dad took his tractor to a small engine , shade tree mechanic for tune-ups , belt changes , etc . He was a very nice older gentleman , but he didn't know how to adjust the variator . It went unadjusted for probably 25 years & wore unevenly & suffered resulting corrosion . If it had been kept properly adjusted I have little doubt it would be completely functional today .