Cranks over but no start!

[SaskBigGreenMachine]

So the truck wouldn't crank over yesterday, ignition would switch on, i was able to turn the key and hear the click before the starter would crank, but nothing would happen after the click. I could depress the clutch pedal back and forth and hear the click but nothing would crank over. So I went and replaced the starter today. Got everything connected back up and go to start it up and it cranks over but now it won't start. As it's cranking over there is a constant clicking sound that is being made as the truck cranks like the sound of a starter once the batteries have been drained, yet the batteries aren't even close to being dead. I'm stumped, all i did was replace the starter. The truck started and ran fine two days ago and now there is nothing. Help if you can cause I'm lost on this one.