I'd check your coolant level.. Charlie has a good point because the trans fluid is usually cooled in the bottom of the radiator and I've head of some cases where the trans fluid will leak into the coolant or even coolant into your tranny Also, if this is a vacuum problem you should be able to take apart your air cleaner and see that it is soaked in fluid. Do you notice excessive smoke in your exhaust? That's a sign of burning ATF.