Brand Name:
Toyota
Model Number:
U250E
Function: Engages overdrive (O/D) gear by applying hydraulic pressure to clutch pack in planetary transmissions (e.g., 4L60E, A340E).
Key Features:
Material: Billet aluminum with micro-polished bore (surface finish Ra ≤0.8μm)
Seal Design: Dual-lipped HNBR or Viton for high-temp stability (>250°F)
Bleed Circuit: Quick-release channels prevent clutch drag
Failure Modes:
Seal Roll-Over: Improper installation causes pressure leaks (O/D slippage)
Bore Scoring: Contaminants jam piston (delayed O/D engagement)
Fatigue Cracks: Stress fractures near apply lugs (sudden O/D loss)
Critical Specs:
Piston-to-bore clearance: 0.03-0.07mm
Apply pressure: 55-85 psi (varies by transmission)
Pro Tip: Lubricate seals with petroleum-free grease during assembly – petroleum degrades rubber.
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