chances are your hydro is toast... but, you can check several other things: 1) look to see if your park brake caliper (located on the outside of the tranny housing) assy is frozen up ( a few shots of brake shoe cleaner fluid will free it up).. 2) with the deck removed and the rear jacked off the ground, chk the traction belt and pulleys for proper operation (BE CAREFUL)..3) lastly, you can remove the tranny in it's entirety; turn it over & drain the old oil from the top breather hole (will take a day or so) - catch all the old oil so as to know how much to refill; purge to eliminate air; retest. understand 20w-50 is a good replacement. good luck.