DTC P0730 Transmission Incorrect Gear Ratio

This Diagnostic Trouble Code (DTC P0730) is relevant to the automatic transmission in the vehicle. P0730 states “incorrect gear ratio”. Fortunately this is a code that the retail auto parts stores don’t immediately try selling parts to the potential customer.

Many times this code indicates that the transmission may need to be replaced, rebuilt or overhauled which can vary between $2500 and $5000. This code is far too generic to be of use in a repair situation, however armed with this code we can make some general inspections to see if some maintenance can repair the problem for considerably less money.

A test drive is our best choice of diagnostics but before we go on that test drive check the fluid level and conditions per the manufacturers’ instructions in your owners manual. Eg: Jeep vehicles should be checked with the transmission in the neutral position and of course on a level surface. Remember to take adequate safety precautions like applying the park brake, etc.

Make note of the fluid condition, clean and pink or burned and brownish. Wipe the dipstick with a white paper towel and look for particles in the fluid. If the fluid is low then add fluid but under no circumstance should the fluid level exceed the full level on the dipstick.

Before going on the test drive, shift the transmission selector from neutral to reverse and neutral to drive several times and notice any latency in the engagement of the gears. Reverse is typically slower to engage.

On the test drive pay close attention to the shift points for all the gears, and notice any slippage or any other problems under different throttle pressures.

When you return from the test drive wipe the dipstick again and notice if any particles have reappeared. Look for bubbles in the fluid also. Excessive particles in the fluid usually indicates a transmission that needs replacement.

You should check for Technical Service Bulletins (TSB) including those that address the possible need to reprogram the Powertrain Control Module (PCM) that may relate to the Diagnostic Trouble Code (DTC P0730). If it needs reprogrammed that can be performed with J2534 tools such as ours.

If no problems were encountered on the test drive and the fluid was dirty and burned from age or lack of maintenance it’s a good idea to flush the fluid with some fluid exchanger. You may want to precede the fluid exchange with a cleaner to clean the transmission and especially the valve body of gum and varnish deposited from the old fluid. At the same time replace the filter assembly and this also allows for a thorough examination of the transmission pan for debris and excessive metal pieces.

The amount of fluid used in a thorough exchange usually varies between 12 and 18 quarts per vehicle and this is controlled by the equipment manufacturer not the vehicle. It is a good idea to replace the fluid with a synthetic especially if it was organic fluid from the factory as it is only a small price increase difference. This is a good gamble to repair the code without replacing the transmission and typically costs about $200 to $250.

If shifting problems were encountered on the test drive, depending on what they were and the severity you may be able to replace just the valve body with an updated remanufactured one and overcome the DTC P0730 and repair the shifting problems. This repair can cost from $500 and up.