55204 – Hydro-Gear O-Ring #137 Square Profile 2.05" x 0.099" (OEM-Spec) The Hydro-Gear 55204 O-Ring (#137, 2.05" x 0.099") is a genuine OEM-spec sealing component engineered for use in Hydro-Gear hydrostatic transmissions, pump assemblies, and other high-pressure hydraulic systems. Designed to precise dimensional tolerances, this square-profile O-ring provides robust sealing performance between mating surfaces to prevent fluid leakage, maintain hydraulic pressure, and protect internal components from contamination. Built to Hydro-Gear’s exact specifications, the 55204 O-ring ensures long service life and dependable operation in demanding turf and drive applications. Product Details Manufacturer Part Number: 55204Brand: Hydro-Gear (OEM-Spec)Part Type: O-Ring Seal (#137, Square Profile)Dimensions: 2.05″ ID × 0.099″ Cross-SectionProfile: Square (rectangular sealing profile)Function: Hydraulic and fluid-system sealingMaterial: Durable elastomeric compound (application-specific)Application: Hydro-Gear hydrostatic transmissions and pump systemsOEM Status: Genuine Hydro-Gear replacement part Function Provides a reliable fluid seal between mating surfaces in hydrostatic systems Prevents hydraulic fluid leakage at high-pressure interfaces Maintains proper system pressure for smooth and efficient operation Protects internal components from dirt, moisture, and contamination intrusion Supports long-term durability and consistent performance in turf equipment Compatible With The Hydro-Gear 55204 O-Ring is used in select Hydro-Gear hydrostatic systems, including: Hydro-Gear integrated transaxles Pump and motor assemblies requiring square-section sealing Transmission or hydraulic interfaces that specify a #137 (2.05″ × 0.099″) seal OEM parts diagrams and repair kits calling for part number 55204 Note: Always verify compatibility by cross-referencing your Hydro-Gear transmission or pump model with the official Hydro-Gear parts breakdown before ordering. How It’s Used This square-profile O-ring installs between two mating components to create a fluid-tight seal: Remove old seal: Drain hydraulic fluid and clean the service area. Clean surfaces: Ensure sealing surfaces are free of debris, nicks, or burrs. Lubricate O-ring: Lightly coat with hydraulic fluid or appropriate assembly lubricant. Install: Carefully seat the Hydro-Gear 55204 O-ring into its groove or sealing surface. Reassemble: Align and secure mating components per service instructions. Refill fluid: Refill with proper hydraulic fluid and test system operation. Proper installation and surface preparation are key to effective sealing and leak prevention. Suggested Maintenance Inspect hydraulic sealing areas during service intervals for fluid seepage Replace O-rings whenever related components are disassembled Keep hydraulic fluid clean to reduce premature seal wear Avoid using damaged or stretched O-rings during reassembly Use only OEM-spec Hydro-Gear seals for correct fit and long-lasting performance The Hydro-Gear 55204 O-Ring (#137, 2.05″ × 0.099″, Square Profile) is a dependable OEM-spec sealing solution designed to prevent leakage, maintain pressure, and support long-term performance in compatible Hydro-Gear hydrostatic transmissions and hydraulic assemblies.
