Slips in First Gear

WARNING: This page is about a different car, the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

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