GM Service Manual Online
For 1990-2009 cars only

Slipping or Rough 1-2 Shift

Checks

Causes

Valve Body Assembly

    • Mislocated valve body to spacer plate checkball or checkballs.
    • 1-2 Shift valve train stuck due to sediment
    • Gaskets or spacer plate incorrect, mispositioned or damaged
    • 1-2 Accumulator valve stuck or damaged
    • Face not flat
    • 4-3 sequence valve stuck or damaged
    • #1 or #8 checkball missing or mis-located
    • 1-2 accumulator valve bushing rotated 180°

2-4 Servo Assembly

    • Apply pin too long or too short
    • 2nd servo apply piston seal missing, cut or damaged
    • Restricted or missing oil passages
    • Servo bore in case damaged

2nd Accumulator

    • Porosity in 1-2 accumulator cover or piston
    • Piston seal or groove damaged
    • Nicks or burrs in 1-2 accumulator housing
    • Missing or restricted oil passage
    • 1-2 accumulator piston spring not seated
    • Rough finish in 1-2 accumulator bore in case
    • A cracked 1-2 accumulator piston - allowing fluid to leak by

2-4 Band

Worn or mispositioned

Oil Pump Assembly or Case

Faces not flat