With as many miles, as I have on my vehicle, parts will wear out.
Since I have owned the vehicle:
Two transmissions, the first shortly after I bought the truck. I knew it was on it's way out though, and had already priced a new transmission. This transmission lasted roughly 85,000 miles, I believe it wore out early due to "ridge racing" and "mudding". While the second one and current transmission has roughly 154,000 miles on it and still strong!
Three clutches due to above mentioned conditions, I give this Bronco II every bit of punishment I can dish out while off-road. I'll be installing a fourth clutch very, very soon. Planning to install a double or triple plated clutch due to extreme conditions.
Front drive axle, one broke after going up a rock hill climb.
Ball joints have worn out several times, due to the fact my truck is never kept in alignment. Reason again is above mentioned driving conditions.
Rotors and brakes, have worn slightly earlier than expected. Again due to, what I believe, can be blamed on mud getting between pads and the rotors.
Also the parking brake cable to the rear brakes, had been apparently pulled off. I think this was also due to off-road conditions.
The above mentioned is due to extreme conditions while the drive train components may have failed over the amount of time. And such things as brakes and other miscellaneous things.
Only recently has the valve cover gaskets started to leak. Worst thing about this is the oil is leaking onto the exhaust headers, this cause the oil to be simple burned off. So when I come to a stop, I can smell the oil burning and slight signs of smoke rolling out sides of hood.