P0734Generic code

P0734 Code: Gear 4 Incorrect Ratio

The P0734 code means that with 4th gear engaged, the ratio between the transmission input and output speeds is not correct, so something is slipping. Causes run from low fluid to worn clutches. The fluid level and condition tell you whether the repair is cheap or a rebuild.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$100 to $4,000
Difficulty
Hard
System
Transmission
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0734 code means

The transmission computer knows the ratio of every gear. It divides the input shaft (turbine) speed by the output shaft speed and compares the result with the theoretical ratio. If the value does not match for a period of time with 4th gear engaged, it concludes that an internal clutch or brake is slipping and stores the P0734 code.

Before you think about an internal repair, rule out the simple things: fluid level and condition, a solenoid or valve that is not giving enough pressure, and the speed sensors (a sensor with a wrong signal creates a false ratio).

With any transmission code, the first check is the fluid: the correct level using the manufacturer procedure (often with the engine running and at a specific temperature), a red or pink color, and no burnt smell. Low or degraded fluid causes slipping, harsh shifts, and solenoid or gear ratio codes that disappear once you correct it.

If the slipping is real and the fluid smells burnt, the 4th gear clutches are probably worn. Driving on makes the damage worse and fills the fluid with particles that damage the rest of the transmission. See the P0700 guide to understand how transmission codes are read and why you need a scan tool that can reach the transmission module.

P0734 code symptoms

  • Engine rpm that climbs without the vehicle accelerating.
  • Slipping or a late shift when it goes into 4th gear.
  • Limp mode.
  • Burnt fluid smell.
  • Check engine light on.

Likely causes of the P0734 code

  1. Low fluid level. The cheapest cause, so check it before anything else.
  2. Degraded or wrong fluid that loses its friction properties.
  3. Solenoid or pressure valve that does not apply enough pressure.
  4. Input or output speed sensor with wrong readings.
  5. Worn 4th gear clutches or band. The friction material wears away and the gear slips.
  6. Internal pressure leak from seals or sealing rings.

How to diagnose the P0734 code step by step

  1. Check the fluid level and condition.
  2. Read the codes in the transmission module with a compatible scan tool.
  3. Compare input, output and engine rpm in 4th gear.
  4. Run a line pressure test if the transmission has a pressure port.
  5. Inspect the pan. Metal particles or friction material point to internal wear.

How to fix the P0734 code

  • Top off or change the fluid with the specified type.
  • Replace the solenoid or repair the valve body.
  • Replace the speed sensor if it gives wrong readings.
  • If the clutches are worn, repair the transmission.
  • Clear the adaptations, relearn the transmission and clear the P0734 code.

Technical reference data

  • Ratio = input rpm / output rpm.
  • Normal fluid temperature: 70 to 95 °C (158 to 203 °F).
  • Reference values only: check the manufacturer data for your vehicle.

Brand-specific notes

The source says some transmissions have known failures of specific clutches, so look for manufacturer technical bulletins for your model.

P0734 on GM

The GM 6T transmissions have known failures of specific clutches.

P0734 on Ford

The Ford 6R transmissions have known failures of specific clutches.

P0734 on Toyota

The Aisin transmissions used by Toyota have known failures of specific clutches.

P0734 on Nissan

The Jatco CVT transmissions used by Nissan have known failures of specific clutches.

Frequently asked questions about P0734

What does the P0734 code mean?
It means the ratio between the input and output speeds is not the right one for 4th gear. In practice, something inside the transmission is slipping.
Can I drive with a P0734 code?
Only as little as necessary. Slipping creates heat and wear that damage the transmission quickly.
Can the fluid be the cause?
Yes. A low fluid level or degraded fluid causes slipping.
Does the transmission need to be repaired?
Only if the slipping is real and the clutches are damaged. Rule out fluid, solenoids and speed sensors first.
How much does it cost to fix P0734?
Between $100 (fluid, solenoid) and $4,000 (a complete repair).

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