Guide
Gearbox and TCU tuning explained
The transmission control unit (TCU) decides when and how the gearbox shifts. A TCU file changes that behaviour. This guide explains the two levels, what each changes, and what we need from you.
How a TCU works
The TCU reads speed, throttle, torque and temperature signals, then chooses gears and clutch pressures. Many modern gearboxes are controlled by a TCU that is separate from the engine ECU.
A TCU file replaces the transmission calibration. Some gearboxes also need matching engine changes, so we check this when you upload.
Results vary by engine, fuel, condition and supporting hardware, and no gain or outcome is guaranteed.
Gearbox / TCU Stage 1
Pricing: Master file price €65 ex VAT · slave (Tier E) €39.
Stage 1 is the standard TCU calibration. It typically firms up shift timing, adjusts shift points and improves the feel of automatic gear changes.
It does not change the mechanical strength of the gearbox. The clutch and internals stay as they are.
- Send the TCU read with the correct part number.
- Tell us if the gearbox has had a clutch, valve body or fluid change.
- Say if you tow, as this affects the torque limits we set.
Common codes
P0700Transmission control system malfunction. The transmission control system has logged a fault. Read the stored codes in the TCU for detail.P0730Incorrect gear ratio. The gear ratio measured from the speed sensors does not match the gear selected.P0715Input or turbine speed sensor circuit. The TCU does not see a valid speed signal from the input or turbine sensor.P0740Torque converter clutch circuit malfunction. The TCU reports a fault in the torque converter clutch circuit.
Gearbox / TCU Stage 2
Pricing: Master file price €76 ex VAT · slave (Tier E) €46.
Stage 2 adds calibration for launch behaviour, torque limiters and clutch pressure. It suits drivers who use the car harder and have upgraded the drivetrain.
Stage 2 raises the torque the gearbox is asked to handle. Only choose it if the clutch, gearbox and driveline can take that load.
- Tell us the clutch and any drivetrain upgrades.
- Describe the use: road, track, towing or off-road.
- Confirm whether the car has a limited-slip differential.
Common fault codes
Codes vary by make, model and ECU. Read the stored codes on your own car before and after flashing.
P0700Transmission control system malfunction. The transmission control system has logged a fault. Read the stored codes in the TCU for detail.P0730Incorrect gear ratio. The gear ratio measured from the speed sensors does not match the gear selected.P0715Input or turbine speed sensor circuit. The TCU does not see a valid speed signal from the input or turbine sensor.P0740Torque converter clutch circuit malfunction. The TCU reports a fault in the torque converter clutch circuit.
Questions about gearbox and tcu tuning explained
Do I need an engine file with a gearbox file?
Often yes, because the engine and gearbox share torque information. We check this when you upload and tell you before you pay.
What is the difference between TCU Stage 1 and Stage 2?
Stage 1 refines shift behaviour. Stage 2 adds launch, torque limit and clutch calibration for drivetrains that can take more load.
See emissions-related files All questions
Emissions-related files are supplied for off-road, competition, agricultural and export use only, and must not be used on public roads.