My oldest EXMARK, TT1448HP has a speed problem. I would guess this machine is 6-7 years old. (gosh, it has no hour meter)It had a new motor about 4-5 yearsago.The problem is, it doesnt have any ground speed. We have owned this unit since it was new. Can the pumps just wear out? I have complained to the dealer for a few years about thisproblem. I ran this mower yesterday and it seems it has gotten worse. Any Help???