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P0730 Incorrect Gear Ratio

The ratio between input and output shaft speed doesn't match any gear the transmission should be in — it's slipping or not engaging properly.

Transmission

The module compares input shaft speed to output shaft speed. That ratio should match the gear it commanded. P0730 means it didn't. Either the transmission is genuinely slipping, or it never actually shifted into the gear that was requested, or one of the two speed sensors is lying.

Diagnose P0730 on your specific vehicle Add your year, make and model for ranked causes, repair videos and the exact parts you need

Can I keep driving?

Driveable

Get it diagnosed promptly. It will often be in limp mode. Continuing to drive a slipping transmission is how a repairable fault becomes a rebuild.

How serious

High. Real slipping generates heat and wears clutches quickly, and it tends to get worse rather than plateau.

Symptoms you'll notice

What causes P0730

Ordered by what to check first — how likely each cause is, weighed against what it costs to rule out. Working down the list in order is what stops you replacing an expensive part to fix a cheap problem.

01

Low or burnt transmission fluid

The first and cheapest thing to check. Low fluid causes real slipping, and burnt fluid tells you the clutches have already been overheating.

02

Failed shift solenoid

A solenoid that doesn't actuate means the commanded gear never engages, so the ratio never matches.

03

Faulty input or output speed sensor

Worth ruling out before assuming mechanical failure — a sensor reporting wrongly makes a healthy transmission look like it's slipping. Compare both sensors on live data.

04

Worn clutch packs or bands

The genuinely mechanical answer, and the expensive one. Typically means a rebuild.

05

Valve body or hydraulic pressure fault

Insufficient pressure means clutches apply partially and slip under load.

How to diagnose it

  1. Check fluid level and condition following the manufacturer's procedure.
  2. Read all transmission codes, since P0730 rarely appears alone and its companions narrow things down.
  3. Compare input and output speed sensor readings on live data across a range of speeds to verify the sensors themselves.
  4. Calculate the actual ratio in each gear and compare against spec to see which gears are affected — one bad gear points at a specific clutch or solenoid, all gears points at pressure or fluid.
  5. Check for metal debris in the fluid or on the pan magnet, which indicates internal wear.

Parts you might need

Tools for the job

Related trouble codes

Get the parts list for your vehicle Ranked causes, tutorials and live part prices for your exact year, make and model

Fitment matters. Causes and parts above are the common cases for P0730 across vehicles. The specific part numbers, procedures and torque specs vary by year, make, model and engine — always confirm against service data for your vehicle before buying parts or starting work.