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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 16 (Automatic Transmission - 4L60-E/4L65-E/4L70-E - Service, Diagnosis & Troubleshooting) >> Slips in First Gear

Slips in First Gear

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Slips in 1st Gear

Checks Causes
Forward Clutch Assembly (646-651)
  • Clutch plates worn
  • Porosity or damage in forward clutch piston
  • Forward clutch piston inner and outer seals missing, cut or damaged
  • Damaged forward clutch housing
  • Forward clutch housing retainer and ball assembly not sealing or damaged
Forward Clutch Accumulator (353-358)
  • Piston seal missing, cut or damaged
  • Piston out of its bore
  • Porosity in the piston or valve body
  • Stuck abuse valve
Input Housing and Shaft Assembly (621) Turbine shaft seals missing, cut or damaged
Valve Body (60)
  • 1-2 Accumulator valve stuck
  • Face not flat, damaged lands or interconnected passages
  • Spacer plate or gaskets incorrect, mispositioned or damaged
Low Roller Clutch (678)
  • Damage to lugs to inner ramps
  • Rollers not free moving
  • Inadequate spring tension
  • Damage to inner splines
  • Lube passage plugged
Torque Converter (1) Stator roller clutch not holding
1-2 Accumulator Assembly (55-57, 104)
  • Porosity in piston or 1-2 Accumulator cover and pin assembly
  • Damaged ring grooves on piston
  • Piston seal missing, cut or damaged
  • Valve body to spacer plate gasket at 1-2 Accumulator cover, missing or damaged
  • Leak between piston and pin
  • Broken 1-2 Accumulator spring
Line Pressure Refer to Oil Pressure High or Low .
2-4 Servo Assembly (13-28) 4th Servo piston in backward