01-07-30-030
Automatic Transmission - Harsh 1 to 2 Gear Upshift Diagnostic Information
October, 2001


Subject:  Diagnostic Information on Harsh 1-2 Upshift

Models:  2001-2002 Passenger Cars and Light Duty Trucks with 4L60-E or 4L65-E Automatic Transmission


Recently, a product improvement analysis study was undertaken to determine the causes of harsh 1-2 shift concerns in 2001 model year 4L60-E automatic transmissions.

The product improvement analysis study was completed on transmissions which met the following criteria:

• Transmissions with a consistent harsh 1-2 shift were obtained from vehicles in service.
• These transmissions had a consistent harsh 1-2 shift, not an intermittent condition.
• The transmissions had 19,000 km (12,000 mi) or less.

The consistent harsh 1-2 shift condition was verified during a test drive by dealership personnel, before the transmission was removed.

• The transmissions were disassembled and carefully inspected to identify causes of the harsh 1-2 shift.

The study pointed out that the following four conditions were found to cause the majority of harsh 1-2 shift comments:

1. 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.
   
2. 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.
   
3. A cracked 1-2 accumulator piston (56) that is allowing fluid to leak by.
   
4. 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 of 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 busing rotated 180 degrees.
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. 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

The diagnostic table shown above is newly revised.

This diagnostic table should be used when addressing a harsh 1-2 shift concern.  The revised document, ID # 10224, will be found in the next update to the SI2000 database.