To check the hydraulic fluid on a Troy Bilt Zero Turn, you will need to locate the dipstick on the side of the transmission. With the engine off, remove the dipstick and wipe it clean with a rag. Reinsert the dipstick and screw it in until it is snug. Remove the dipstick again and check the level of fluid. The fluid should be at or near the full line on the dipstick. If it is not, add hydraulic fluid until it reaches that level.