CAT 370-3205 Articulation Hitch Cap

CAT 370-3205 is a Cat® Parts end cap assembly used by Caterpillar for hydraulic systems. It is commonly found in the main valve cover, cylinder end cap, or pump body end cap of medium and large excavators and loaders. Its core function is to seal the hydraulic cavity, fix the internal valve core/piston, withstand high pressure and prevent oil leakage, and ensure the stable operation of hydraulic components. It is a key sealing and positioning component of the hydraulic system. The following is structured technical and application information:

Core Technical Parameters

Item Details
Basic Attributes
Model 370-3205 (End Cap Assembly), Type: Flange-type hydraulic end cap, Material: Cast aluminum alloy (ZL109, T6 heat treatment, hardness HB 120-150), Surface anodized (thickness 0.01-0.02 mm), Single weight approximately 1.8 kg, Working pressure ≤35 MPa (5075 psi), Working temperature -40℃ to +120℃, Sealing type: Combination seal (nitrile rubber O-ring + PTFE retaining ring), Protection rating IP67, Design life ≥10000 hours (normal operating conditions)

Key Dimensions
Flange outer diameter 152.4 mm (6 inches), Mounting hole distribution circle diameter 127 mm (5 inches), Number of mounting holes: 6, Hole diameter 11 mm (bolt M10×1.5), End cap thickness 25.4 mm (1 inch), Sealing groove diameter 101.6 mm (4 inches), groove width 5.3 mm, groove depth 2.8 mm, inner diameter 88.9 mm (3.5 inches, tolerance 0/+0.02 mm), flange flatness ≤0.02 mm, thread accuracy 6H. Compatible Models and Parts: Compatible with Cat 336D2 and 349D2 excavators (main control valve end cover), 966M loader (boom cylinder end cover), 320D2 hydraulic pump end cover; compatible with 370-3206 O-rings, 370-3207 retaining rings, M10×30 socket head cap bolts, flat washers (10 mm), lock nuts (M10).

Performance Parameters: Sealing pressure 35 MPa, burst pressure ≥52.5 MPa, leakage ≤0.01 cm³/min, oil resistance meets SAE 10W-30 oil standard, aging resistance ≥5000. Bolt preload torque 35-40 N·m (hours)
Structural and Performance Advantages:
The cast aluminum alloy material undergoes T6 heat treatment, combining lightweight and high strength, suitable for high-pressure hydraulic conditions. Anodized surface enhances corrosion resistance and reduces the risk of oil contamination.

The combined sealing structure (O-ring + retainer ring) is suitable for high-pressure reciprocating or static sealing, effectively preventing oil leakage. The PTFE retainer ring reduces O-ring wear and extends seal life.

The flange design ensures precise installation and positioning. Bolt tightening guarantees a tight seal, adapting to various cavity sealing needs in hydraulic valves, cylinders, pump bodies, etc., offering strong versatility.

Installation and Maintenance Points: Before installation, clean the end cap sealing surface and cavity, checking for scratches, deformation, and rust. Replace with new O-rings and retainer rings, and apply a small amount of hydraulic oil to lubricate the seals.

Tighten the bolts evenly and in a crisscross pattern (in three stages, with pre-tightening torques of 15 N·m, 30 N·m, and 35-40 N·m respectively) to ensure uniform stress on the flange surface and prevent localized deformation that could lead to leakage.

Maintenance: Check the end cap tightness every 2000 hours. If oil leakage is detected, immediately stop the machine and replace the seals. It is recommended to replace them simultaneously with the O-rings and retaining rings to ensure a good seal.