Second Gen Speedometer

[Lunatech]

I got to wondering, if I were to put different final drive gears or taller or shorter tires on my '96 wagon it would naturally make the speedometer incorrect, right? But in the gen 2 cars it is controlled by a VSS through the ECU, I think. If that is so can the problem be corrected by flashing the ECU? It is an OBD2 vehicle, I've never dealt with this kind of thing, it just seems that there should be something in it that indexes the final drive or tire parameters. Or, maybe there are different VSS's for different ratios. Or should one be looking to the TCU?

Anybody out there know anything about it?

[Legacy777]

I think on the OBD2 vehicles you could probably just adjust a paramter in the ECU....or so one would think.

[ciper]

Auto or manual?
From what I know the manual transmission is a direct connection from the speed sensor to the dash while for an auto its through the TCU to the dash. Speedometer adjustment comes from the gear inside the transmission which drives the head and from the TCU generating the right signal.

[Lunatech]

Automatic

[ciper]

Then I am pretty sure the TCU takes the signal from the speed sensors and then outputs a signal thats the same as a five speed would output on its own. If you didn't change anything and put a TCU from a 96 outback I bet your speedo would show 9% higher speed