| Subject: | Diagnostic Information on MN8, MT1 SES/MIL Illuminated, DTC P0757, Harsh Shift, Delayed 2-3 Shift, 2-3 Shift Flare, No Third Gear, Slips in Third Gear or Reverse |
| Models: | 2002-2007 Chevrolet Avalanche 2500 Series, Silverado Classic, Suburban 2500 Series |
| 2002-2008 Chevrolet Express |
| 2002-2007 GMC Sierra Classic, Yukon XL 2500 Series |
| with HYDRA-MATIC® 4L80-E (RPO MT1) or 4L85-E (RPO MN8) Automatic Transmission |
The purpose of this bulletin is to provide technicians with additional diagnostic information on DTC P0757. Refer to Service Information (SI) for DTC P0757, 2-3 Shift Solenoid Valve Performance - No Third or Fourth Gear.
Additional 4L80-E or 4L85-E transmission symptoms may be a harsh shift, delayed 2-3 shift, no third gear or slip in third or reverse, or a 2-3 shift flare. The transmission fluid inspection may or may not indicate distressed clutches.
On all 2002-2006 vehicles and certain 2007-2008 vehicles, check for any debris caught in the #11 check ball. If debris is found, repair per Service Bulletin 08-07-30-001. Also inspect the direct clutch for damage that may have been caused by
a leak in the oil circuit that may be a result of the debris. If no debris is found, and no other cause is found when referring to Service Information (SI) for DTC P0757, valve body replacement may be indicated.
Also check the 2-3 shift valve for debris or leakage. If none of these items seem to have a concern, replace the 2-3 shift solenoid due to a possible sticking pintle.
