is my crankshaft bad?

[93burb]

I have a 93 Suburban 4x4, in the morning when I put it in gear mainly to move forward, I give it gas and you can hear the engine reving up, but it takes a few seconds before it kicks in gear. I recently had my transfer case replaced and I asked the mechanic to check my transmission. The mechanic said my transmission was ok. about two weeks later, another mechanic told me that my crankshaft had to be replaced because of a whistling, whining noise he heard when you rev up the engine. My suburban also has this nocking noise while running which sounds like my rockers or something. The nocking sound speeds up as you accelerate. I'm no mechanic and I don't want to be taking advantage of. Can someone tell me what my symptoms sound like? Is it my crankshaft or transmission?

[bad68chev]

Could also be lifter noise. Can you tell if its coming from top or bottom of engine? Oil level ok?

[93burb]

I checked the trans. oil and it was low so I added some and it seamed to go away for awhile, then about two weeks later it started doing it again. There doesn't appear to be no leak, no stain in the parkway either. It only does this in the morning when I first start it up, during the day it seams to work ok, although I do feel it lacks power it doesn't hesitate on acceleration. How can I check to see if it is the lifters? Or anything else for that matter?