'94 K1500 Starting Troubles

I have been around for the past days cruising the net for answers for our truck. I'm not the mechanic in the family (my dad is). Everyone he has asked doesn't believe that the truck could do what it is doing. It will start up only when the front is jacked up, then it can be driven (until we shut it off). While on the ground, it does make a clicking sound. My dad has tried changing the battery, checking if it is the oil, and other things also. Does anyone have any ideas what the problem may be?

First thing to check is the starter-take it off and in to autozone or checker etc. to have it tested. Or you could always smack the starter with a hammer while trying to start it. Do this carefully with the wheels blocked and of course in park. The only thing I can think of that would respond like this to a change in angle on a 94 would be the starter. Or you could just change the starter. I have several chevy trucks so I keep spare parts around for testing purposes. If it is not the starter please post again with a more detailed description of the problem. (How high do you have to jack it up, what noises if any does it make, when you turn the key does it draw current?)