Last Friday I visited the JD dealer about buying a subframe for my 4210. I had a lengthy discussion with the salesman, service manager and parts tech regarding the subframe. To make a long story short, the backhoe does not mount on the subframe. It actually mounts on two "rockshaft assist mounting plates". These plates bolts on the transmission/rear axle housing. The subframe is bolted on the frame to strengthen it from the backhoe use. BTW the 4210 model does not require a subframe...which is another story of it's own /forums/images/graemlins/crazy.gif.