2000 GMC 2500 Pickup Q&A

2000 GMC 2500 Pickup Question: Installed a rebuilt 4l80e tranny, speedometer doesn't work & shifts hard?

speedometer work but doesn't show full speed and must feather gas to make shift. Tranny shop says loose connection, checked all connection still no work -
Answer 1
Vehical speed sensor and connections between it and PCM can cause this. Also if alternator starts putting out a/c voltage it can do this too. VSS is on the transmission or transfer case if its a 4X4. -
Comment 1
how do you check vss? I checked the connections and everything seems tight. I still have the old tranny, should I remove th speed sensor and install in rebuilt unit? -
Comment 2
with a volt meter on a/c voltage scale or a lab scope. Faster the turn of out drive the more a/c voltage it puts out. With a lab scope it senda wave form that intencefies the faster shaft turns. -