GMC Repair: Tach, Speedometer, Trans acting up!, vehicle speed sensor, gmc sierra

Question
It is a '95 GMC Sierra K1500, 4WD, 350, Automatic

My Tach, Speedometer like to go on an off. When they go off a lite come on that says check gauges. Also when this happens the tran. does not shift.  any help would be nice.  Thank you!  

Answer
Hi
The transmission and speedo COULD be the VSS (Vehicle Speed Sensor) and or related wires. The Tach is a seperate circuit that gets signal from Distributor and power is fed through the "Gauges" fuse. The only way I see them being a related concern is either The ground (G200) and is located Behind the left side of the IP, below the fuse block, on the tie bar. the other way would be the IP cluster itself.
I think you MAY have 2 issues. I would get the VSS checked and make sure your getting a signal to the VSS buffer (located next to the PCM, around the glove box area). Make sure the buffer is sending the signal out. A Scan tool SHOULD be able to assist you in this. If there is NO VSS signal the transmission will not shift properly, if at all.
Also your speedo will drop off with no VSS.
As stated, this is just advise from experience and published material.
If in doubt, please take it to a Repair shop in your area your familiar with.
Good Luck
Paul