The engine was running. i turned it off to get something. came back and it wont start. All lights come on bright , engine makes a single loud click and wont turn over.

Is this a loud click or a quiet click? Is it a single click or lots of fast repeating clicks? A quiet single click is most likely the starter relay in the fuse box failing. A louder single click is related to the starter motor, the starter solenoid or related parts. A repeating, rapid clicking is usually a power supply issue. Is there any warning lights on the dashboard? Were you having any other issues before this happened?
Try going back to basics. You may have already tried some of these.
Check the battery is the correct one for your vehicle and is fully charged. A V8 engine takes a lot of effort to physically turn over and a weak or wrong battery will struggle to turn the engine over. Check all the connections on the battery are clean and secure. Check the other end of each battery cable is also clean and secure. A bad electrical connection can drain the battery so it doesn't have enough power for the starter.
Apply the park brake and put the vehicle in Neutral. Try starting the vehicle. This disconnects the transmission making it easier for the engine to turn over. Does that make any difference? Comment below with more information and I'll try to help you more.

Is it a single loud click when you try to start it? Or multiple clicks or "buzz"? If it is a single click heard from the engine, your starter has likely failed. Test the battery first, and inspect the battery cables/connections for any looseness/corrosion.

Battery very weak
Alternator not working
Bad connections at battery posts, or bad connections on ground cable

If you can jump the car to start it, and it will stay running, take it to Advance Auto, Auto Zone, O'Reilly's, etc and have them test your battery/alternator.

sounds like you blew your engine... something probably broke inside causing it to not be able to turn over.

BEST WAY TO TELL IF YOUR STARTER IS BAD. FIRST MAKE SURE YOUR BATTERY IS GOOD,ARE YOUR LIGHTS BRIGHT ECT? IF BATTERY IS LOW YOU WILL GET A STUTTERING NOISE FROM RELAY NOT A SINGLE CLICK. THE FACT YOU ARE GETTING A CLICK RULES OUT THE IGNITION SWITCH. USE A TEST LIGHT (CAN BE PURCHASED AT ANY AUTO PARTS STORE FOR A COUPLE OF BUCKS. GROUND LIGHT ON SOMETHING METAL ON YOUR ENGINE WHERE YOU CAN STILL REACH THE STARTER. TEST THAT THE LIGHT IS WORKING BY PROBING BIG RED POWER WIRE ON STARTER. IF LIGHT LIGHTS THEN YOU HAVE A GOOD GROUND. IF NOT LOOK FOR ANOTHER GROUND. ONCE LIGHT IS PROVED WORKING,HAVE SOMEONE TURN KEY TO START POSITION WHILE YOU PROBE THE SMALL IGNITION WIRE ON THE STARTER SOLENOID . IF THE LIGHT LIGHTS THEN MOST LIKLY THE STARTER IS BAD. YOU SHOULD ALSO BE AWARE THAT IF YOUR CAR CAME EQUIPT WITH A DISABLED LOCTRONICS DEVICE FROM THE DEALER YOU NEED TO REMOVE THAT FROM THE SYSTEM. I FOUND THIS OUT THE HARD WAY .....BUT THEN AGAIN YOU WOULDN'T BE GETTING ANY CLICK FROM THE START POSITION SO ITS PROBABLY NOT THAT ANYWAY. IF YOU GET NO LIGHT AT THE STARTER SOLENOID IGNITION WIRE THEN YOU HAVE A BAD FRAME SOLENOID MOST LIKELY.

I HOPE I HAVE BEEN SOME HELP:)

I'd feel best if you can find a reputable mec and have it looked at. There are a mess of things that can make loud noise. You could have anything from a bad berring to a blown engine. When your'e on the road remember go to someone who is reccomended or a national chain or dealer..

if the lights are bright and you hear a clicking and your heat blows good, the head lights are still real bright after trying to start a few time replace the starter (you can try to hit the starter with a hammer otr somthing heavy a few times and then try to start if it sounds better or starts replace the starter) if the battery goes dead try to jumpit if it starts then dies after a few min its the alt if it starts runs good and you let it run for about half hour shut it off and it wont restart rite away its the battery.

your torque converter could have went. i feel its definetly your trans. i need more input

The starter solenoid will click when the battery is to low to start the car. Have the battery charged and load tested to make sure it's good. Check the charging system to make sure the alternator is good. Check the wire connections at the starter. If either is loose, the starter won't work.
With a full, known good battery, turn on the headlamps and try starting the engine. If the headlamps stay bright, the contacts in the solenoid are bad. If the headlamps dim greatly or go out, the starter is shorted out and must be replaced.
Also try turning the crankshaft manually with a breaker bar and socket if you suspect that the engine may have seized up.
Charlie

Does it make the loud click just once, or will it continue to click when you turn the key?
If it is just once, then there is still a bad connection someplace for the main power. If it continues to click every time you turn the key to "start", then it is probably the starter solenoid itself that is bad. There are two big terminals (bolts) on the solenoid, and if you connect a 12V test light or meter across them, you should see power there. If the light doesn't go out (or very dim) when you turn the ign. to 'start', then the solenoid is bad. If the light goes out and the starter doesn't turn, then there is something wrong with the starter. I suspect the solenoid also because it works better with a strong charge on the battery.