I have 25 hours on this lawn tractor. It worked fine pulling hills last summer. It suddenly and without warning, stopped. It will start up the hill and then slowly stop on the hill and make a shuttering sound that sounds like it's coming from the idler pullies. If I put the transmission into "trim" it will sometimes pull the hill, but very slowly. I don't have any trouble out of it on level ground or slight inclines.

It is under warranty and the service facility replaced the transmission and drive belt (although they couldn't find any problem with it). No difference after that; still won't pull hills. They told me that it wasn't designed to pull a 15 degree slope and my slopes are probably about 15 degrees. My question: why did it work last summer and not now? Also, if this is indeed a safety feature, how can I disable it? Is it internal to the transmission? If so, could I somehow change the angle that the transmission is mounted with spacers or something? This mower is useless to me in it's current condition.

Any help is appreciated.
Thanks.

I can grant you that without cause, mtd did not warranty this old transaxle. There has to be some probable cause, or they will not warranty it. Carry it back to the shop.

I have the same lawn tractor with the same problem. The drive belt slipped of the transaxle pully and fell between the pully and housing. I had to wedge it back in place. I have 12 hours on my mower.