It is an '01 3/4 ton chevy with a 6.0. The speedometer is jumping around and the transmission will act up along with it, shifting down to 3rd, then back up to OD. The brake light is coming on when this happens also, like the ABS is getting bad inputs. Is this a VSS problem, or possibly something else. Where is the VSS? Some things have said there are 2 VSS on the 4l80e. Are these on the tranny or one in the transfer case? Does this truck have a separate transmission computer or is it controlled by the PCM? Any insight would be helpful.

Thanks in advance.

 

It sounds like a VSS problem. The VSS is in the rear of the transmission (2wd) or in the transfercase (if 4 wheel drive).
You are getting ABS codes also because on trucks they get the rear signal from the transmission instead of the rear axle.

Check for a bad connection or possibly also replace the VSS.

 

I need to scan the code, but there is what looks like a VSS on the side of the tranny and a sensor on the transfer case. Not sure what is what or which is the speed signal.

 

the rear sensor(oss) is the one you want.the front is for drum speed.