Wet brakes run in oil,keeps them cool under heavy use,as turning with brake at end of field. wet brakes will last longer,require less adjustments and so on. They are internaly mounted meaning if you have to replace your have to drain trans.oil. most wet brakes are a multibile disc set up making more stoping power. Dry are mostly single disc or drum will heat under heavy use and wear more quickly,but are a slight bit faster to replace,not as much stoping power. the wet brakes are the better set up. but on a tractor you should not replace brakes for a very long time any how. most tractors gear or hydro will al most stop themselfs if you let of throtle or hydro peddle.