uno

My 95 2500 chevy loses power to the tack,speedo,trans and shift indicater when the truck starts up. when the key is in the run position but not running there is power at the trans fuse and gear indicater light up normaly until I start the moter. when the gear light is on my trany works until the light goes out then it get stuk in 3ed gear.I replaced the gages and ecm all ready any other ideas