I have a 2011 D140 with 109 hours on it and the last month when going up a hill it starts to slow down considerably but then it seems to kick in and takes off. Could this be a stretched belt ? Or does it sound like the hydrostatic transmission? My lawn is roughly a 1/3 of an acre with 50% of it fairly steep. I take very good care of it by changing the oil, filter, air filter and greasing it every 15-20 hours. Any thoughts would be appreciated.
My D110 was doing the same thing (180 hours / 5 years old), even on level ground. I ended up lifting the seat/body (remove seat springs and the four screws that hold down the dashboard) enough to get to the rubber cap/plug thing at the rear of the diff (turns out it's a prv). Removed the prv and filled the diff up with diff oil from AutoZone ($16 a gallon). She's running great, cut two lawns, no sign of any leaks (even the axle leak has stopped), and no more jerky reverse...I think the diff was low on oil when I first bought the unit 'cause she's never cruised smoother and quieter.