P077F
Reverse 2 Incorrect Ratio
Some transmissions provide a second reverse ratio (typically a slower crawler reverse for trailer manoeuvring or hill descent). The TCM detects that the input/output ratio in this gear does not match its calibrated value — slipping clutch or wrong gear actually engaged.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: hard
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Common causes
Ordered by how often each turns out to be the cause.
- Slipping clutch in reverse 2 elementCommon
Parts involved
- Clutch Pack
- Friction Band
P077F is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.