P0734 - Gear 4 Incorrect Ratio
The transmission control module (TCM) has detected that the gear ratio for 4th gear is out of the expected range. This indicates internal slippage or a mechanical failure within the transmission, often caused by worn clutches, a faulty torque converter, or low transmission fluid pressure. The code is set when the TCM compares input and output shaft speeds and finds a mismatch for 4th gear.
01. Most Common Causes
- Low or contaminated transmission fluid
- Worn or burnt clutch packs in 4th gear
- Faulty shift solenoid or valve body issues
- Internal transmission damage (e.g., broken bands, planetary gear failure)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or delayed shifting when engaging 4th gear
- Transmission slipping or revving high without acceleration
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Check transmission fluid level and condition; top off or replace if necessary.
Step 2: Scan for additional codes and perform a transmission pressure test.
Step 3: Inspect wiring and connectors to the transmission control module and solenoids.
Step 4: Perform a stall test and road test to verify slippage in 4th gear.
Step 5: If internal failure is suspected, remove transmission pan and inspect for debris; consider professional rebuild or replacement.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, driving with P0734 can cause further transmission damage and lead to complete failure. It is best to have it diagnosed and repaired immediately.
How much does it cost to fix?▼
Costs vary widely: a simple fluid change may cost $150-$250, while a transmission rebuild or replacement can range from $1,500 to $4,000 or more.