Hydrostat filter is Napa 1487 or Fram C1678
Apparently its a very old number that hasn't been used in anything for quite some time. My local Napa showed only one in stock at their warehouse and it was old packaging and covered with a very thick layer of dust.
It wouldn't hurt to change the fluid and filter but I doubt that's the cause of your trouble as the filter is in the reservoir. I would look closely at the hydrostat belt tension. Someone else recently mentioned sluggish performance and thought he had no belt slippage. When he pushed on the belt while it was running he reported the tractor took off.
Edited by Canawler, February 01, 2014 - 06:33 PM.