I realize this is an old post but just some additional info regarding 4WD. I have a JD X728 which is all-wheel-drive (runs the front wheels all the time without the ability to disengage it). I have a flat lawn and initially spent the extra on the AWD for the possibility of pushing snow in the winter. What I found is that the AWD on this unit is awesome for cutting grass - even on a flat, dry lawn.
JD does this on the newer (last few years) X7* AWD models via hydraulic drive to the front differential. With a metering valve mechanically linked to the steering, they then spin the outside front wheel faster than the inside front wheel. This eliminates the scuffing you would otherwise get when turning if you had a standard full 4WD and you can't even tell this unit is in 4WD, other than the main benefit - full traction all the time!
What's really cool is that I can turn at corners at full speed and don't get any 'pushing' of the front end. I also don't get any wheel spin when starting or skidding when stopping. This thing steers to exactly where you point it, moves exactly when you tell it to, and stops on a dime - all the time. If you are out there to relax and don't care how fast it takes to cut your lawn, not necessary, but when your time is limited like mine, this is a big plus.
If you're looking to convert something over to 4WD, hopefully this will shed some light on some of the potential pit-falls which JD has addressed in these new models.
FYI - I had a zero turn which too was real fast but wasn't nearly as comfortable as this rider.
JD does this on the newer (last few years) X7* AWD models via hydraulic drive to the front differential. With a metering valve mechanically linked to the steering, they then spin the outside front wheel faster than the inside front wheel. This eliminates the scuffing you would otherwise get when turning if you had a standard full 4WD and you can't even tell this unit is in 4WD, other than the main benefit - full traction all the time!
What's really cool is that I can turn at corners at full speed and don't get any 'pushing' of the front end. I also don't get any wheel spin when starting or skidding when stopping. This thing steers to exactly where you point it, moves exactly when you tell it to, and stops on a dime - all the time. If you are out there to relax and don't care how fast it takes to cut your lawn, not necessary, but when your time is limited like mine, this is a big plus.
If you're looking to convert something over to 4WD, hopefully this will shed some light on some of the potential pit-falls which JD has addressed in these new models.
FYI - I had a zero turn which too was real fast but wasn't nearly as comfortable as this rider.