VSS Signal to TCM. Which VSS?

[rrres]

This is regarding my 99 V70XC with AW50-42LE AWD:

This past couple of weeks, I noticed that my reverse gear suddenly developed a slip when pressing on the accelerator. I hooked up Vida and it showed "CDM-0001 VSS Signal Missing", which I'm thinking might have something to do with the slip.

I'm confused. When I do a search, The terms VSS, Vehicle Speed Sensor, Wheel Speed Sensor, ABS sensor, and etc. show up. Some show the sensor on the transmission and some refer to the one on the knuckle. I recently replaced the one on the right steering knuckle with a cheap Rockauto Delphi sensor.

Which VSS is the CDM-001 referring to? Which VSS provides the signal to the TCM?

Thanks.