| Subject: | Diagnostic Tips for Slipping or Missing Second, Third and/or Fourth
Gear |
| Models: | 2001-2002 Chevrolet Camaro, Corvette |
| 2001-2002 Pontiac Firebird |
| 2001-2002 Chevrolet and GMC C/K Pickup and Utility Models (Silverado,
Sierra, Suburban, Tahoe, Yukon, Yukon XL) |
| 2001-2002 Chevrolet and GMC G-Van Models (Express, Savana) |
| 2001-2002 Chevrolet and GMC M/L-Van Models (Astro, Safari) |
| 2001-2002 Chevrolet and GMC S/T Pickup and Utility Models (S10,
Sonoma, Blazer, Jimmy) |
| 2002 Chevrolet and GMC S/T Utility Models (New Style) (TrailBlazer,
Envoy) |
| 2001-2002 Oldsmobile Bravada |
Recently, a study was completed to determine the causes of slipping/missing
2nd, 3rd or 4th gear in the 4L60/4L65-E transmission family. This study was
conducted using transmissions which were determined by dealership technicians
as having a slipping/missing shift. The transmissions used were from vehicles
with less than 19,000 km (12,000 mi) and the slipping/missing shift
condition was verified during a test drive by dealership personnel before
the transmission was removed from the vehicle.
Eight items were found to cause the majority of the slipping/missing
shift concerns. These eight items are listed below in the order of frequency
that they were found.
| • | Chips in the servo feed oil passage, orifice #7 in the spacer
plate. |
| • | Cut forward clutch piston inner seal. |
| • | Cut 3/4 clutch piston outer seal. |
| • | Input housing orifice cup plug blown out. |
| • | Input housing cracked or broken. |
| • | Mislocated valve body to spacer plate check ball(s). |
| • | Case damaged at the 2nd clutch apply piston pin bore causing the
pin to drag/stick in the bore. |
| • | Input housing air bleed orifice cup plug with a check ball that
does not seal. |
In addition to the above items, a misadjusted shift cable has been found
to cause these types of concerns.
When attempting to correct a slipping/missing second, third or fourth
gear, the items listed above should be inspected as possible causes. It is
also important to reference the appropriate Service Information for additional
possible causes of these concerns.
