I have a Duratrac 1800 with power steering. Its done this for a while but not very often. When I'm either mowing or when I'm using the front push blade I sometimes get a rattling noise from the rearend area. It only seems to happen when I'm turning and have a heavy load on everything. Turning up a steap hil or backing up while turning in a tight place. I changed hydraulic fluild and filter just over the winter. It had been doing it before I changed fluid and filter so this didn't help. Any adjustments that may need to be checked?? Ideas?