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

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

by in Melrose, NM on April 18, 2012
1 answer 2 comments
ANSWER by on April 18, 2012
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 by on April 18, 2012
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 by on April 18, 2012
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.