P0734: Gear 4 Incorrect Ratio
12 vehicles · 9 makes · $200-$6,500 repair
Most Reported On
P0734 is an OBD-II diagnostic trouble code meaning “Gear 4 Incorrect Ratio.” This code means the Transmission/Powertrain Control Module detected an incorrect gear ratio in 4th gear. The module continuously compares input shaft speed to output shaft speed; if the ratio in 4th gear doesn't match the expected value, it sets P0734. This usually indicates the transmission is slipping or not fully engaging 4th gear due to a hydraulic, friction, or solenoid problem. Symptoms include slipping, flaring RPM, harsh or missed shifts, and possibly limp mode. This code is most commonly reported on 2007-2012 Hyundai Veracruz, 1996-2002 Mercedes-Benz C-Class, and 1994-2010 Chevrolet Silverado 1500, plus 9 other vehicles, with repair costs ranging from $200 to $6,500.
Common Causes
Typical Repair Cost
Based on 13 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0734, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Vehicles Affected (12)
1999 3.2TL 5-speed auto was the start of the famous Acura V6 transmission failures
3.0CL automatic transmission slips and fails — flush is forbidden, filter is not serviceable
ZF 9-Speed Transmission Hesitation, Hard Shifts and Stalling (2016-2019 MDX)
FAQ
What does P0734 mean?
P0734 stands for "Gear 4 Incorrect Ratio." This code means the Transmission/Powertrain Control Module detected an incorrect gear ratio in 4th gear. The module continuously compares input shaft speed to output shaft speed; if the ratio in 4th gear doesn't match the expected value, it sets P0734. This usually indicates the transmission is slipping or not fully engaging 4th gear due to a hydraulic, friction, or solenoid problem. Symptoms include slipping, flaring RPM, harsh or missed shifts, and possibly limp mode.
What are the most common causes of P0734?
The most common causes of P0734 are: Low or degraded/burnt transmission fluid, Slipping clutch packs or worn friction elements in 4th gear, Stuck or faulty shift solenoid, Valve body / internal hydraulic leak or restriction, Worn or failing torque converter, Faulty input or output speed sensor, Internal mechanical wear (bands, planetary gears). The specific cause varies by vehicle.
How much does it cost to fix P0734?
Repair costs for P0734 range from $200 to $6,500, depending on the vehicle and root cause.
Which vehicles are affected by P0734?
Au7o has documented P0734 across 12 vehicle models from 9 manufacturers: Acura, Chevrolet, Chrysler, GMC, Hyundai, Jeep, Kia, Lincoln, Mercedes-Benz.
Sources (12)
- media2007 Hyundai Veracruz Automatic Transmission Problems - CarComplaints
- articleMercedes 722.6 5G Transmission Valve Body Conductor Plate Replacement - YouCanic
- articleHere's What A 'Conductor Plate' Is And Why It Kills So Many Mercedes Vehicles - The Autopian
- Forum722.6 Conductor Plate Failure - PeachParts Mercedes-Benz Forum
- ForumSOLVED! - Sudden loss of 3rd/4th gear (4L60E) - GMTNation
- ForumTransmission slipping in 3rd gear - SilveradoSierra.com
- articleMost Common 4L60E Transmission Problems & How to Fix Them - Motorverso
- mediaBNB Gears: 4L60E Transmission Failure Points: Symptoms, Fixes
- mediaCherish Your Car: 4L60E Transmission Problems: What Fails, What Survives
- ForumGMT400: 4L60E trouble shooting guide STICKY
- ForumPirate 4x4: 4l60e no reverse
- mediaMonster Transmission: 4L60E No Reverse Causes, Symptoms, and Solutions
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.