What's the difference between TSS & VSS on a 98?

What is the function of the turbine speed sensor and what does it control?

Is the TSS involved when the PCM decides to shift gears?

Is the TSS involved when the PCM enables TCC lockup?

Does "shaft speed sensor" refer to the TSS or VSS?


- no codes, just trying to understand the design - Thanks.

I don't know all the details in the electronic control of the transmission.
From what I read, the TSS Turbine Speed Sensor measures the speed of the tubine shaft, and is used by the PCM to help determine EPC....Electronic Pressure Control...which has to do with how "hard" the shifts are.....and it also used to help the PCM determine the Torque converter engagement schedules.

The Turbine shaft connects between the torque converter and the drive sprocket.....which turns the drive chain.....driving the driven sprocket....
In short.....power from the engine goes to the torque converter, from the torque converter (through the turbine shaft) to the Planetary gears.

So.....the TSS measures the speed of the shaft that is the OUTPUT of the Torque Converter....but the INPUT to the planetary gears...which are manipulated to give the different gear ratios....or the different gears......4 forward speeds, Neutral, and Reverse.

The VSS measures the actual vehicle speed.....and would be a measure of the output speed of the transmission...AFTER the planetary gears.....how fast the drive shafts are turning.
This is also used by the PCM for determination of the EPC pressure, shift solenoid scheduling, and to know what the vehicle speed is.

You got it wiswind!