I understand that these are "obsolete" and that they were supposedly non-serviceable, other than filter and fluid. I am looking for a 311-2600R (right side) Hydro Gear integrated pump/motor combo, or someone that can rebuild/refurb one. The Hustler part # is 788059 and it is the charged version (C-IZT). Drained fluid, replaced filter and drain plug, as well as vent tube. After purging procedure, right tire/wheel is very weak and can be stopped with my hand. Any ideas? Thanks in advance.