P0734: Gear 4 Incorrect Ratio
What to do
Slipping at higher speeds with lower gears feeling normal. Ask whether the fault persists with torque converter lock-up disabled — that check distinguishes a converter problem from a gear problem without taking anything apart.
What this code means
The measured ratio in fourth gear is wrong. On many four-speed automatics fourth is an overdrive applied by its own dedicated clutch, which makes a fault confined to fourth genuinely more contained than it sounds — that one element can often be addressed without disturbing the rest of the gear train.
A specific confusion worth heading off: fourth on such a transmission is frequently where torque converter lock-up is applied, so converter clutch slip and a fourth-gear ratio error present almost identically. Whether the fault survives with lock-up commanded off separates them, and it is a scan tool operation rather than a strip-down.
Likely causes
Start here
- Low or degraded transmission fluid · easy
- Slipping torque converter clutch · specialist
- Failed shift solenoid · moderate
Less common
- Worn valve body · specialist
- Worn clutch packs · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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