| Subject: | 4L60-E/4L65-E Automatic Transmission Diagnostic Information on Harsh 1-2 Upshift |
| Models: | 2001-2006 GM Passenger Cars and Light Duty Trucks |
| with 4L60-E or 4L65-E Automatic Transmission |
This bulletin is being revised to add model years and models. Please discard Corporate Bulletin Number 01-07-30-030A (Section 07 - Transmission/Transaxle).
The following four conditions have been found to cause the majority of consistent, harsh 1-2 shift comments.
| • | Chips/Sediment/Debris/Contamination found in the valve body, 1-2 accumulator valve (371) bore, may cause the 1-2 accumulator valve to stick or hang-up. |
| • | Chips/Sediment/Debris/Contamination found in the valve body, 4-3 sequence valve (383) bore, may cause the 4-3 sequence valve to stick or hang-up. |
| • | A cracked 1-2 accumulator piston (56) that is allowing fluid to leak by. |
| • | Mislocated/Missing valve body-to-spacer plate check balls (61). |
When attempting to correct a consistent harsh 1-2 shift, the four conditions listed above should be inspected as possible causes. It is important to also refer to the appropriate Service Manual for further possible causes of this condition.
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 |
| • | 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
|
| • | A cracked 1-2 accumulator piston - allowing fluid to leak by |
| • | 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 |
|
2-4 Band
| Worn or mispositioned
|
Oil Pump Assembly or Case
| Faces not flat
|
This diagnostic table should be used when addressing a harsh 1-2 shift concern (SI Document ID 10224).
