Hey I have a 1997 gmc sierra c1500 ext. cab 5.7 liter v8...the truck will crank but won't start and the alternator gauge is showing that there isn't any voltage on the battery and I'm thinking there is a bad connection somewhere but not sure. Any suggestions.

a connection would be the first thing to look for ,if thats ok then a fusable link from the starter

If the truck is cranking then the starter is fine and so are the connections. You can try jumping it with another vehicle. Sometimes the battery has enough juice to crank the vehicle but not enough left over for the ecm to operate while the engine is cranking. If jumping it doesn't help then you need to find out whether the truck has lost fuel or spark or both. The alternator will show 0 because when it isn't running it not putting any voltage out. If there was no voltage at the battery then the engine wouldn't crank.