P0734Gear 4 Incorrect Ratio
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- The transmission module divides input (turbine) speed by output speed and compares the result with the ratio of the commanded gear; a deviation means slip – a clutch or brake not holding, too little pressure – or a wrong gear. Thresholds: Ford more than 30 rpm off for 1.8 s three times (diesel 2023: over 20 % for 12 s), GM's 2006 tables and the Allison 1000 converter slip of 200–230 rpm for 2.25 s after one trip, Saab's Aisin boxes over 20 % twelve times without MIL. P0734 concerns fourth gear. A 2006 GM table separates it explicitly from P0730: fourth gear showing the ratio of third is P0730, any other deviation P0734. Slip shows as raised engine speed or no upshift into fourth. On GM manual transmissions it checks the gear position sensor.
- What you may notice
- Slipping or flare in fourth gear, engine speed higher than expected
- Harsh or delayed shifts
- Limp mode (Aisin: second gear and reverse only), transmission warning
- Check engine light depending on manufacturer
- Likely causes
- LikelyFluid level too low or fluid worn or contaminated
- LikelyClutch or brake for fourth gear worn (linings, piston seal)
- PossibleSticking shift or pressure valve, leaking valve body gasket, blocked passages
- PossibleGM manual transmissions only: gear position sensor faulty or not learned
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €3,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.