Hydraulic Gear Pump Seal Kit 3278740 for CAT 312D Excavator | Pilot Charge Pump Repair Set

Restore Pilot Control Pressure & Eliminate Gear Pump Leaks

Hydraulic gear pumps in excavators operate under high rotational speeds and continuous pressure fluctuations. When gear shaft seals and body housing gaskets degrade, pilot control pressure drops—resulting in sluggish joystick response, slow implement engagement, and internal hydraulic oil bypass.

This heavy-duty 3278740 repair seal kit delivers exact pressure containment for main and pilot charge gear pumps fitted to Caterpillar 312D and 312D L hydraulic excavators. Precision-molded to match factory tolerances, every seal in this pack ensures zero-leak seating during sustained high-RPM operation.

Advanced Dynamic Seal & Thermal Engineering

• High-Velocity FKM (Viton) Radial Lip Seal: The primary gear shaft seal utilizes a spring-loaded fluorocarbon lip profile to maintain consistent radial pressure on the spinning shaft, resisting thermal carbonization and lip hardening at temperatures over 120°C.

• High-Modulus P6000 Polyurethane Rings: Engineered to resist pressure spikes, dynamic deformation, and fluid shearing during high-speed gear rotation.

• Anti-Contamination Auxiliary Wipers: Secondary seal lips actively block fine metal particles, slurry, and dust from invading the pump housing, protecting internal shaft journals from scoring.

• Static Casing Gaskets & Heavy-Duty NBR O-Rings: High-durometer Nitrile O-rings create a complete fluid seal across pump body plates, manifold covers, and valve block interfaces.

Target Equipment & Component Compatibility

• Machine Models: CAT 312D, CAT 312D L

• Target Assembly: Hydraulic Gear Pump / Pilot Charge Pump Group

• Part Number Cross-Reference: 3278740 / 327-8740

Technical Specifications

• Kit Type: Hydraulic Gear Pump Overhaul / Rebuild Seal Kit

• Primary Materials: Fluorocarbon (FKM / Viton), Premium P6000 Polyurethane (PU), Industrial NBR Rubber

• Fluid Compatibility: Mineral-based hydraulic fluids, synthetic hydraulic oils, ISO VG 32/46/68

• Application Target: Direct-fit replacement for shop overhauls or field pump servicing

Fitment Verification Notice

Caterpillar 312D excavators may use different gear pump manufacturers across production runs and serial prefixes. Prior to ordering, check the part number stamped on your pump housing or cross-reference 3278740 / 327-8740 in your CAT parts manual to ensure proper component match.