i have a 1995 1500 Silverado that i just replaced the head gasket on motor runs fine but the tachometer does not work now i bought the truck with a bad head gasket so i am not sure if it was working when i go it. The other problem i am having is it the transmission is not shifting in to 2nd i have 1st and reverse. With the trans i was wondering if the tach is connected and that could be the problem. Thanks for any help
Mike
PS this is my first Diesel

Hi mjm609, The tach gets it's signal from the altenator . Should be a 2 wire connector. I don't think it is related to your transmission issue. Have you checked for any codes?problem

I had similar problems and it turned out to be a faulty ignition switch

it is funny that you say ignition switch because that was my next item to replace because the buzzer that goes off when your keys are in stays on when running.

Tach,

Double check the alternator wirng. The tach signal comes from Alternator. (the second wire)

If you have an electronic transmission then the 1 2 shifting solenoid is not either receiving it's signal or it's given up it's ghost. Replacing them is simple enough. Verifying them is just as simple. Find the two leads going into the tranny that belong to the solenoid and test them with a multimeter set on ohms. They should test ~1 to 2 K Ohms.