I have a 1990 trans am gta with the 305 tuned port injection engine. My speedometer only works half of the time. Could this be the cable? or the actual gauge itself? If so, how would i go about fixing this?

 

i believe if IIRC that in 1990 they became electrical.

 

ok if I'm right your speedometer is mechanically driven .... if it is unplug the cable and check for defaults .. if nothing seems wrong it can be your gauge ... what i did to figure it out on my car i used my drill to turn the rod inside so see if it was really the gauge the problem