I have a 2003 gmc envoy xl it has been running fine..drove it all day. Went home 4 hrs later it will not start.. It acts like it is dead but everything from the lights to the heat works fine..I mean it doesn't make a noise no nothing..it has a new alternator and new battery.. But if it's my starter shouldn't I hear a noise?
But if it's my starter shouldn't I hear a noise
Not if the starter solenoid is stuck. This is the piece of metal that connects the circuit and allows the starter motor to receive power. It's usually pulled into place magnetically, thereby connecting two terminals and powering the motor. When solenoids age, they tend to stick, or, in some cases, physically break. Once the bridge no longer works, no power can get to the motor.
To test it, you can temporarily realign the solenoid by hitting it with a hammer a few times and see if it starts after that. Disclaimer: Don't go around hitting random parts of your car with a hammer, if you aren't sure which one is the starter.
If the hammer trick does resolve the issue, it's likely only a temporary fix. Once a solenoid begins to act like this, it's probably going to give a repeat performance sometime in the future. If it sounds like I learned this lesson the hard way, well... yeah. Just assume that this may be the last time the car starts with this solenoid.
One last note: Sometimes solenoids are attached and sold as one piece with the starter, other times they are separate. My Jeep is one piece; my lawn tractor is separate.