I know this is going to sound stupid, but check your ATX fluid level. The level of the fluid will differ depending on the temp of the tranny. It might just be that you are running a little low. You should go ahead and change it while you at it, unless you have changed it recently. Then again, you can never have good enough fluid in there.
I agree on getting codes pulled, just to see. But the VSS is not all that exspensive though.
