2003 Tahoe Z 71 runs great until I take it on a longer trip. Engine just shuts off while driving down the interstate and will not start for hours.

Any recent engine repairs ? Trouble codes ?

try changing fuel filter as it may be clogged. the time you are waiting may allow deposits to settle back in line.

i would first check your surpentine belt to see if it is getting burnt up, most whining sounds are an indication of a bad pully either from the alternator,compressor, pwr steering pump, tensioner, idler pully,ect.ect., i would take the belt off and spin the pullys by hand untill you find wich one is bad

yes ,the engine would had a great pressure inside check as soon as you can the oil level and have it fix ,before it gets worse.

I had a similar problem @105k. I had changed the fuel filter but it was still sending all kinds of codes that were related to 2 problems. Long story short, the main problem was a bad trigger assembly in the distributor (rough running) and the other was a loose engine to body ground (engine code issue). Good luck, this worked for me, now 171k.

check fuel pump relay, on start up, relay is bypassed, allowing a start, but dies when runs out of gas.

You said it's runs fine, but it just won't start after driving a while. If thermostat or temp sensor was bad you'd be overheating. It sounds like a vapor lock. Good luck

You can try the local salvage yard to locate one for you. As for distance, you never know with electronics. It could be like that for an hour or a year or two. worst will not run the engine. Sorry for the bad news. Good luck

it could have a tune up problem cap rotor wires plugs or a idle possision sen is not working is there a check engine light on

I would suspect fuel pump before an odd ecm problem. When was you last fuel filter? An extremely dirty filter will wipe out these fuel pumps if left in play too long.