Reading threw a few posts some say that the VSS is mounted under the dash? I have been looking for it there and can't find no yellow box like described. Haynes manual says it is mounted on the transmission on 85 and later models.

Am going to work so no time to look now but I might need to get under the car loosk like it?

The reason why I ask is I think I might have a bad VSS because when I data log the speed readings surge and drop to normal and surge again.

Could it be a faulty VSS?

The VSS you describe is near the tailshaft on your transmission. As for your problem, I have no idea, but I already gave you the info I have.

The VSS your referring to is mounted on the back of your gage cluster. Remove the cluster and you will see the yellow VSS parts. If it were '90 or later it would be mounted where the speedometer cable goes into the transmission.

Firebirds switched to a trans-mounted VSS earlier, 85 I believe is right; Camaros kept the yellow box behind the dash much later.

If your car is an 85 Camaro, it will have the behind-the-dash type.

Follow the spedo cable coming off the trans. It will run towards the dash. Where the cable ends is your vss buffer box that you need.

Yep mine is a 86 camaro and I remember seeing the yellow box on the back of the dash. I thought there might have been another VSS somewhere.

Does anyone have any ideas on what could be causing the speed to jump up and down like that? I am pretty sure the Needle on the speedo gauge does not surge and only the speed that the ECM sees when I data log surges.

Any ideas? A bad connection in wiring? Stripped gear in the transmission?

I have a spare VSS module off a 145mph speedo gauge. Could I use that VSS in my 85mph gauge or are they both calibrated differently?

I could be wrong but i thought the speedo was still a mechanical type and worked off the cable, and the vss box was just for the cpu.

Dankhound yes that is correct the VSS is just for the ECM