Parts
$50-3000+
P0734 — Gear 4 Incorrect Ratio
CAUTIONIs it safe to drive? 4th gear isn't holding the right ratio — slipping in overdrive. Highway driving risks overheating the transmission; have it diagnosed.
What P0734 means
The TCM sees the wrong ratio in 4th gear (often the overdrive gear). 4th-gear clutch pack slip is a common failure on higher-mileage automatics. Exact details vary by make.
Most likely causes (in order)
- Worn 4th-gear / overdrive clutch pack
- Low or burnt transmission fluid
- 4th-gear related shift solenoid
- Speed sensor error
- Overdrive brake band (band-type transmissions)
Symptoms you might notice
- RPM flare at highway cruise in top gear
- Overdrive hunting
- Limp mode
What to check first
Watch RPM at steady highway speed — a slow RPM creep upward in 4th = classic overdrive slip. Check fluid; if it's dark and burnt, internal damage is likely.
Repair cost & difficulty
Labor
3-20+ hr
Difficulty
Shop job