They run the range of really old to newer. After posting, I also went to check out on our heavy equipment. And again.. found every type of mounting scheme thinkable... side of engine, mid engine.. ( some mid engine mouns had the battery higher than the engine, even with fuel tank.. so engine wasn't pushed forward..e tc... lets see.. under foot rests, ahead of foot rest, lower side of engine, front lower side of engine, directly in front of radiator..go figure... in front of radiator, but lower to not block it.. , under seat, behind seat
stradled on either side of tranny, under , before or after foot rests... ok thats it.. That is from everything from a lawn tractor to 50's and 60's era tractors, to larger industrial tractors from the 70-90's, and some small non-name brand inports from the 90's ( eicher, mahindra, etc ).
As for problems with the tranny... just depends on the setup... on my NH .. the tranny, is below and forward of the operator.. but then.. I have a cushing glide seat .. so no room there.
One thing I noticed.. with the various combinations of mid-mount batteries.. they obviously has the shortest run to the starter/alternator connections... less BIG copper to route around on the tractor... I really like that.
Soundguy