GM Service Manual Online
For 1990-2009 cars only

Slipping or Rough 1-2 Shift

Checks

Causes

Valve Body Assembly (60)

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

2-4 Servo Assembly (13-28)

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

2nd Accumulator (55-57, 104)

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

2-4 Band (602)

Worn or mispositioned

Oil Pump Assembly (4) or Case (103)

Faces not flat