Just completed a 6MT swap on your Subaru and the speedometer is not working? This is not unusual and you may have also noticed that you had a spare connector left over at the transmission.
Why it happens
Older non-CANBUS Subarus (GC/GF and GD/GG Impreza, SF/SG Forester, BE/BH Liberty and Outback) get their speed signal from a vehicle speed sensor (VSS) on the gearbox.
Later model CANBUS equipped cars don’t have a vehicle speed sensor. Subaru removed the VSS from the gearbox and used the ABS wheel speed sensors for the speedometer instead. Gearboxes like the TY856 6-speed, found in the Gen 4 Liberty and 2008+ STi, are built this way.
If you swap one of those gearboxes into an older car, there is no sensor to produce the signal, therefore the speedometer does not operate.
This can also cause issues with the vehicle tune as the ECU has different map tables for a stationary car compared to a moving one.
The fix
One option is to add the original speed sensor equipment to the new gearbox. This requires new genuine Subaru parts (a speed sensor, sensor shaft and drive gears). It also requires the full transmission to be torn apart to disassemble the front diff and housing to fit these parts. The front housing must also be taken to a machine shop to add the provisions for the sensor. This requires a substantial amount of money and time to ensure it is done correctly without damaging the transmission.
But there is an easier way! Save time, money and remove the risk of damaging your expensive gearbox by using the Rev Match Engineering ABSvss Vehicle Speed Module.
The ABSvss module reads the front ABS sensor and works out vehicle speed, then sends it to the cluster in place of the missing VSS signal. It can be calibrated for non-factory tyre sizes, larger or smaller.
Suitable for the following vehicles:
Subaru Impreza GC/GF (ABS models only) (MY99+ only, 3 wire VSS connector)
Subaru Impreza GD/GG
Subaru Forester SF & SG
Subaru Liberty BE/BH
Note for automatic cars: The module is for factory manual cars. An automatic vehicle must be converted to manual (3-wire VSS) wiring first.
Install and calibration
Installation is plug-and-play and takes less than an hour to complete, no cutting, soldering or any permanent work is required to the car and it is fully reversible – not that you’ll want to go back once you’ve upgraded to a TY856 6MT!
Once installed calibration is easy with a single adjustment to accommodate for any tyre size.
Ready to get your speedometer working again? Get ABSvss here!