Hello guys
I have a 1997 gmc sierra 3500/454/4l80e. It has started shifting erratically and also has not been indicating speed correctly. torque converter lock up is cycling. I changed trans filter/change fluid. Scanned for codes, no powertrain codes up. I jacked up truck and ran up to speed speedometer still not indicating correctly. I put DVM on transfer casespeed switch and it appeared to read correctly
ac voltage increased with wheel speed about 600 mv@ 45 mph. I have nothing to compare that to,also my manual shows two VSS, one also on transmission but the component I think is it has different color wiring . Anyone know what /where that sensor is? thanks in advance Cort

 

well I replaced both vss and still no fix. no codes up but still ****ting all over the place and speedo still not right. I am thinking PCM any ideas ...any one. Come on throw something out there thanks cort

 

try posting in the chevy silverado area, there are more guys that browse over there

 

thank you !