not sure on how the linkages operate in rear end....
just wondering if someone ran rear of tractor into something (going at a good speed and ran into a brick wall for example), causing pressure of linkage arms to go right through the cylinder....
or tried to toss a chain around a tree, and left enough slack in chain and took off fast for a "snap", that instead of chain or linkage arm damage, it caused casing to fatigue and/or crack.
once above was done to get a micro crack going....
thinking thermal expansion was final lick, that caused the final break down. more so if tractor was worked pretty good a few hours before hand, getting all the metal and hyd oil and entire tractor warm.
*rubs chin* normally after a good work out on tractor (running highest gear possible, highest RPM's possible) and really working the tractor, will just not turn off tractor and walk away, but will get RPM's down low to idle, and maybe even drive at a lower RPM if real worked transmission before hand. to let everything have a chance to cool down, via, radiator, hyd oil coolers. and let that coolant workout out those high temperature spots. then shut unit down after say 5 to 10 minutes after the cool down doings. just like regular exercising and keep your muscles from cramping up, you do a "cool down session" same like thing for tractor. to prevent them pin point hot spots from over heating different areas.
there be a reason why tractors have active coolant, (fans, radiators, hyd oil coolers) but once tractor gets shut down, that all goes away....