Gear 4 Incorrect Ratio
The P0734 code means the vehicle's onboard diagnostic system has detected: Gear 4 Incorrect Ratio. This is a critical severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $200 - $4000 (parts and labor)
Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.
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Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.
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Common Symptoms
- Check Engine Light illuminated
- Slipping in fourth gear (overdrive)
- RPM flare at highway speed
- Reduced fuel economy
- Transmission overheating
Probable Causes (Ranked by Likelihood)
- Worn fourth gear clutch pack or overdrive band Very High
- Faulty overdrive solenoid High
- Valve body issue in overdrive circuit Moderate
- Torque converter clutch slipping Low
Step-by-Step Diagnostic Procedure
-
Monitor fourth gear ratio with speed sensors
-
Check overdrive shift solenoid operation
-
Perform line pressure test in fourth gear
-
Check torque converter clutch apply
-
Internal transmission inspection needed if clutch packs are worn
Common Fixes by Vehicle
What techs usually find when diagnosing P0734 on specific vehicles — tap your vehicle for the fix and the exact part:
2007-2018 GM Silverado/Tahoe 6L80E Easy (fluid), Advanced (rebuild) DIY
4th gear ratio error on the 6L80E is almost always internal clutch wear -- specifically the 3-5-reverse clutch pack. This is an overhaul-level repair. Before committing to a rebuild, verify the code isn't being caused by a failing torque converter (lockup chatter can trigger ratio codes). Check for RPM flare during 3-4 shift -- a flare confirms clutch slippage.
Labor: 30 min (fluid), 10-12 hours (rebuild)2005-2016 Dodge Ram/Charger 545RFE Easy (fluid), Advanced (rebuild) DIY
The 545RFE 4th gear uses the overdrive clutch pack. Ratio errors are caused by worn clutch plates or a failing overdrive solenoid. Check for TSB 21-011-14 which covers solenoid pack replacement on 2012-2016 models. A fluid and filter change with ATF+4 may temporarily improve symptoms. If the converter is dragging, the overdrive clutch overheats and fails prematurely.
Labor: 1 hour (fluid + filter), 8-10 hours (rebuild)2001-2014 Honda Accord/Civic Automatic Easy (fluid), Advanced (rebuild) DIY
4th gear ratio fault on Honda 4-speed and 5-speed automatics indicates 4th clutch pack failure. This is a late-stage transmission failure -- by the time 4th gear slips, the transmission typically needs a full rebuild. Check for 4th gear shudder under light throttle as an early symptom. Honda remanufactured transmissions are often more cost-effective than aftermarket rebuilds.
Labor: 30 min (fluid), 8-10 hours (rebuild/replace)Frequently Asked Questions
Can I drive with code P0734?
Drive short distances only. An incorrect gear ratio indicates the transmission is slipping or not engaging properly. Continued driving can cause catastrophic transmission failure.
Does P0734 mean I need a new transmission?
Not always, but often. If the cause is a worn clutch pack or band, a transmission rebuild or replacement is typically necessary. If a solenoid or valve body is the cause, repair may be less extensive.
How is gear ratio measured for P0734?
The TCM compares input shaft speed to output shaft speed. The calculated ratio should match the expected gear ratio. When the ratio deviates beyond a threshold, the code is set.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0734 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
See All Codes & Fixes for Your Vehicle
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