We own a 252-H and today we drove it around- and things were fine (both forward and in reverse). After we heated the transmission fluid up we removed the drain plug (bottom side) and reservoir cap (white) topside. We proceeded to drain all the fluid out and did so successfully. Once we began to re-fill the reservoir it only took about an 1/8th to 1/4 of a quart. Per the directions we ran new 20 weight through the reservoir with both the drain plug and cap off until it stopped draining. Once the reservoir wouldn't accept any more oil (which again was about an 1/8th to a 1/4 of a quart, we screwed the cap back on, started up the tractor, waited about 2 minutes..........and the tractor would not move, neither forward or backward. Can anyone tell us if the system has to be pressurized in some way to engage the transmission, if so how, and why the transmission took nowhere close to what the manufacturer's specifications called for. WE DID not remove what was called a "Vent Plug" at anytime during the above steps, but is a step listed in the manual. Is their a filter for the transmission? Normally the tractor cannot be pushed but after adding the fluid it could be pushed freely (what does this mean).Please help we need to cut the grass bad, thank you very much.