Working on the truck now and just about to reassemble, but wasn't sure if the valley pan rattles loose like the valve covers do. Do they need snugging up? and could they cause a vaccuum leak?

 

Valley gasket can leak oil in the rear if the little bolt for the middle clamp is loose. Or the rubber gasket that goes on the valley lip is omitted.

Valve covers leaking can leak onto the valley gasket also.

Valley gasket can also leak antifreeze and the antifreeze can find its way into the crankcase.

 

Thanks, I was down to the valley pan last night and it seemed to be in good shape (??? from what i could see). There was an obvious oil leak seeping out of both VC's, which I haven't snugged down since I bought the truck two years ago. I do know that all of these gaskets and seals were redone after a headgasket job right before I bought it. So I will see if the tightening of the VC's stops the leak.