The 4L60E/4L65E automatic transmission used on 2003-07 cars and trucks may experience a condition of slipping, late or missed shifts in 2nd, 3rd and 4th. An internal transmission disassembly may reveal a 2-4 band and/or a 3-4 clutch being distressed.

Based on engineering transmission quality reviews, the following items should be inspected and or replaced as required. These items were found to be the cause of the distress to the 2-4 band and 3-4 clutch.

TIP: First check transmission fluid level. This transmission is very sensitive to low oil level.

Also check:

- Low Line pressure (perform a PCS test as defined in SI)

- 1-2 accumulator piston cracked or broken

- 2-4 Servo Piston

- 2-4 Servo Apply Pin for being nicked, scored, binding in the pin bore

- 2-4 Servo Piston Bore for being scored or mismachined

- 2-4 Band Anchor Pin (41) missing (low mileage)

- Servo Feed Oil Passage blocked with sediment

- Forward Clutch Apply Piston Seals for being cut or damaged

- Forward Clutch Apply Piston for being cracked

- Turbine shaft oil seal rings for cut or damaged.

- 3-4 Clutch Apply Piston Seals for being cut or damaged

- 3-4 Clutch Apply Piston for being cracked

- 3-4 Clutch and Forward Clutch oil feed passage blocked or restricted (should flow check the housing, and inspect the passages for proper location)

- 3-4 Clutch and Forward Clutch Turbine Shaft Sealing Rings for being damaged or missing

- 3-4 Clutch check ball (620) for leaking

- 3-4 Clutch air bleed orifice cup plug (698) is in place

- Overrun Clutch Seal (632) damaged

- No. 7 Checkball for not being seated or leaking

- 4-3 Sequence Valve (383) undersized

- Boost Valve (219) stuck causing low line pressure

- Input Sun Gear to Input Carrier Thrust Bearing (700) damaged, came apart

- Selective Washer (616), extra washer installed

- Oil Pump Body (200) cracked, damaged

Also inspect to see if the rear stator shaft bushing (241) is worn on one side or damaged. The turbine shaft (621) may also be damaged in the stator bushing journal area.

This condition may be caused by the stator shaft (214) being non-concentric with the pump cover (215). If this condition is encountered, the pump cover should be replaced along with any residual damage.

If none of the above items are found to be the root cause for the failure, the Input Housing, Forward Clutch Piston and 3-4 Clutch Piston should be replaced and resealed as well as resealing the 2-4 Servo.

Full sized trucks and utilities should have the shift cable properly adjusted and/or replaced if the cable is not holding proper adjustment.

In the event the transmission as a repeat 2-4 Band or 3-4 Clutch Failure, after following the above information, the transmission should be replaced.

Team ZR-1
True Custom Performance Tuning