OBD-II Code · Transmission
P0734
Gear 4 Incorrect Ratio
Severity
high
Left alone, this one tends to take other parts with it.
Can you drive it
Not for long
Driving on this one risks further damage. Get it to a shop rather than carrying on with it.
Indicative cost (USD)
$500–$3,500
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
4th gear ratio fault.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Slipping in 4th
- No overdrive
Likely causes
- Worn 4th gear clutchMost common
- Solenoid
Read the full diagnostic procedureP0734 sets when the TCM commands 4th gear (typically overdrive on a 4-speed, direct or first overdrive on a 5-6 speed) and the calculated ratio is ou…
P0734 sets when the TCM commands 4th gear (typically overdrive on a 4-speed, direct or first overdrive on a 5-6 speed) and the calculated ratio is outside the expected 4th-gear window by 5-7% for the dwell time. On a 4-speed, 4th is overdrive (typical 0.69-0.72:1) and the apply element is almost always the overdrive band or overdrive clutch, both of which are wear items, P0734 in this context is the textbook symptom of overdrive-band burn or overdrive-clutch-pack failure. On 5-6 speeds, 4th is typically a direct or near-direct ratio and the apply elements vary.
Cheapest-first
- ATF level and condition at spec temp, then line pressure under load (4th gear pressure is often lower than lower gears, but should still hit 80-120 PSI at light throttle), then scan-tool ratio monitoring during a 3-4 upshift, the ratio should drop from 1.00 (or thereabouts) to the 4th-gear value cleanly without flare.
- A flare (engine RPM jumps before the ratio settles) confirms slip in the apply element.
- Expensive misdiagnosis: do not authorize a rebuild without first checking for a stuck TCC solenoid, a stuck-on torque-converter clutch in 3rd combined with a healthy 4th can mimic a P0734 if the TCM logic confuses TCC state with gear state, also a $60 TCC solenoid replacement sometimes clears the code on platforms where the TCC solenoid and 4th-gear apply share fluid paths.
Vehicle-specific patterns1994-2007 Ford 4R70W/4R75W (F-150, Mustang, Crown Vic) is famous for overdrive-band burn, the OD band wears as a maintenance item and replacement at…
- 1994-2007Ford 4R70W/4R75W (F-150, Mustang, Crown Vic) is famous for overdrive-band burn, the OD band wears as a maintenance item and replacement at 150K is preventive;
- 2001-2007Chrysler 42RLE (Dakota, Liberty, 300, Charger) sees P0734 from OD clutch-pack wear, Chrysler TSB 21-001-07 covers the updated clutch-pack hardware;
- 2005-2010Honda Odyssey/Pilot 5AT (BGRA, BYBA) has known 4th-gear apply issues tied to torque-converter lockup damage propagating to the 4th-clutch pack, Honda Service Bulletin 11-033 covered affected VINs with extended warranty.
Estimated repair$350 to $4,500.
Look up another code
P0734 — frequently asked
What does a P0734 code mean?
4th gear ratio fault.
What causes a P0734 code?
Common causes: Worn 4th gear clutch; Solenoid.
What are the symptoms of a P0734 code?
Typical symptoms: Check engine light; Slipping in 4th; No overdrive.
Is it safe to drive with a P0734 code?
Not for long. Driving on this one risks further damage. Get it to a shop rather than carrying on with it. Estimated repair: $500-$3,500.
How do I diagnose a P0734 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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