OBD-II trouble code
P0733: Gear 3 Incorrect Ratio
On traditional four-speeds and many five-speeds third is direct drive, meaning the two shafts should be turning at exactly the same speed — which makes this the one ratio code you can confirm with a scan tool and almost no arithmetic. Confirm that your transmission is one of them first: on a six-speed or above, third is a reduction gear and the shortcut gives the wrong answer.
Quick facts
- System
- Powertrain
- Category
- Transmission
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $0 – $3,600
- DIY difficulty
- Advanced DIY
Browse every code in P0700–P0799, or start from the full code library.
What does P0733 mean?
P0733 reports that while third was commanded, the measured relationship between input shaft speed and output shaft speed was not what third should produce. What makes this gear different from its neighbours is how third is achieved mechanically on a great many transmissions, and that difference gives you both a free verification test and a much sharper way to read companion codes.
On most traditional four-speed and many five-speed automatics, third is direct drive: a ratio of exactly one to one. It is not produced by gear teeth at all. Instead, two members of the planetary gearset are locked together so the entire assembly rotates as a solid unit and the input shaft turns the output shaft at identical speed. That single fact is worth more than any diagnostic chart, because where it holds it reduces the check to a comparison rather than a calculation. It does have to be established rather than assumed: on six-speed and higher transmissions third is a reduction gear and direct drive sits further up the box, so the one-to-one expectation would be flatly wrong and would condemn a healthy unit. Where third is direct, put input and output shaft speed side by side in live data, get the transmission into third on a road test with a passenger reading the screen, and compare the two numbers. If they are the same, third is holding. If input speed is meaningfully higher than output speed, something in there is slipping and the code is telling the truth. No other gear in this family can be checked that way, because every other gear requires you to look up a ratio and do the arithmetic.
The second consequence of direct drive is more subtle and it changes what you should suspect. Locking a planetary set solid requires two elements applied at the same time, not one. Those elements are not exclusive to third — each of them is also used to produce other gears. So a slip in third does not identify a single component the way a slip in a reduction gear might. Instead it hands you a logic problem, and the way to solve it is to look at what else is stored. If P0733 is the only ratio code present, suspect the element that third uses and its neighbours do not. If P0733 arrives together with a ratio code for another gear, stop thinking about third specifically — the fault is almost certainly the element those two gears have in common, and a repair aimed at third alone will not touch it.
Third also sits at a particular kind of shift. On many designs the two-to-three change is clutch-to-clutch: one element is released at the same moment another is applied, and the overlap between them is controlled by timing and pressure rather than by any one-way device. That makes third-gear complaints far more likely than other gears to present as a flare between shifts rather than a steady slip once the gear is engaged. A brief rise in engine speed during the shift, followed by a normal, solid third gear, is a timing and pressure symptom, not worn friction material. On vehicles with adaptive shift learning, that is worth acting on before anything else: a transmission that has adapted its shift timing around a previous problem, a fluid change, or a battery disconnection can produce exactly this, and resetting the adaptive values and letting it relearn costs nothing and occasionally clears the whole complaint.
Common causes
- Adaptive shift learning holding stale values after a repair, fluid change or battery disconnection
- Low fluid level or fluid past its useful service life
- Clutch-to-clutch shift timing off, producing a flare between second and third
- Valve-body wear letting apply pressure fall away during the overlap of the shift
- Slipping in one of the two elements that must apply together to lock the planetary set
- An element shared with another gear failing, which sets ratio codes for both
- Shift solenoid slow to respond, delaying one half of the shift
- Input or output speed sensor reading inaccurately and faking a ratio error
Symptoms
- Engine speed flaring briefly during the shift into third, then settling normally
- Input and output shaft speeds not matching in third on a scan tool
- Ratio codes for third and another gear stored together
- Slipping under load in third on an incline or with the vehicle loaded
- Complaint appearing shortly after a fluid change or a battery disconnection
- Failsafe mode locking the transmission into a single gear
- Fluid temperature climbing higher than usual on a long run
- Check engine light with the engine running exactly as normal
Diagnostic steps
- 1.Ask what work the vehicle has had recently. A fluid change, a battery disconnection or any transmission repair can leave adaptive shift values stale, and resetting them and driving a relearn cycle is the one outcome on this code that costs nothing.
- 2.Check fluid level and condition on the manufacturer's procedure, at the specified temperature. Low or degraded fluid produces this code and is the cheapest real repair.
- 3.Confirm from service data whether third is direct drive on this transmission before using any one-to-one comparison. On four-speeds and many five-speeds it is; on six-speeds and above it is not, and assuming otherwise turns a healthy unit into a condemned one.
- 4.Compare input and output shaft speed against the correct published ratio for third, with a passenger reading the scan tool or the session recorded for review afterwards.
- 5.Establish whether the complaint is a flare during the shift or a steady slip once third is engaged. A brief rise in engine speed that settles into a solid third gear is a timing and pressure symptom; a ratio that stays wrong while cruising in third is a holding fault. They lead to different repairs.
- 6.Read every stored code. A ratio code for another gear alongside this one points at the element the two gears share rather than at third, and any repair aimed at third alone will not touch it.
- 7.Work out from service data which elements apply together to produce third, and which other gears use each of them. That mapping is what turns two ratio codes into one suspect.
- 8.Measure line pressure against specification where a test port exists, since a general pressure shortfall affects the overlap of every clutch-to-clutch shift.
- 9.Inspect the fluid for friction material before authorising internal work — glitter in dark fluid means the damage has already spread beyond one element.
- 10.After any repair or relearn, drive a full cycle including repeated two-to-three shifts, warm, and confirm the code does not return.
Repair cost
$0 – $3,600
The floor is genuinely zero here, which is not true elsewhere in this family: if the complaint is a flare on the two-to-three shift and the transmission has recently had a fluid change, a repair or a battery disconnection, resetting the adaptive shift values and driving a relearn cycle can resolve it at no cost beyond the scan tool time. Past that, a fluid and filter service is $150 to $350, a solenoid or speed sensor $200 to $600 fitted, and a valve body $400 to $1,200. If a friction element is worn the unit comes apart, which is $2,000 to $3,600 and up. Pay attention to whether other gears have ratio codes as well, because that changes the estimate substantially — a shared element that has failed is generally deeper in the transmission and a bigger job than one that serves a single gear.
Estimate your repair
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Open the Repair Cost Estimator with transmission fluid service preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an advanced DIY job. It typically requires specialty tools, scan-tool access, lifting equipment, or careful sequencing to avoid causing new failures. Plan for extended downtime and have a backup vehicle. Most owners are better served by a shop that has done this repair before.