So I take my 88 Coupe DeVille in for an oil pan gasket, Mech. says it's the intake manifold gasket that's leaking. O.K. fix it. After a week I pick it up & I hear this faint winding sound Hmmm. what is that? I get to a stop light & she downshifts hard! whoa! Now the shop is closed, so I take in the morning (Sat.) and the owner's son says O.K. we'll check it out. I'm wondering what could cause that? It's not an oil related issue .Arrrgh.