You most likely have a non-serviceable tranny. Most of the trannies that are in these mid level lawn tractors (LT's) are simply not serviceable and require replacement if a major problem occurs. Some guys have actually removed the tranny from the tractor and drained/replaced the fluid by tipping the tranny upside down and draining from the original fluid fill hole which is located on the top side of the tranny. Check your owners manual and you'll likely see a reference that says something like "transmission is sealed and is non-servicable". You need to step up to a GT (Garden Tractor) in order to get a serviceable transmission, one with a removable filter and drain plug. The type of fluid used varies quite a bit (some use tranny fluid, some use motor oil) but you should always use whatever is recommended by the tranny manufacturer.
This message was modified Jul 3, 2010 by FrankMA
Toro Wheel Horse 522xi GT, Honda HS928TA, Honda HS621AS, Honda HS520A, Toro CCR3000 (work in progress), Honda HS624WA (sold 08/23/2010), Stihl BR550 Backpack Blower, Stihl MS250, McCulloch MS1635, Honda EM6500SX Generator