Also found a TSB for torque convertor drain back check ball concern. TSB # 04-07-30-017B However, this is for a 4T65-e. The TSB mentions somewhat your concern. When I go to move it once in a while I jump in start it and put in reverse and nothing. Same with drive. If I put it back into park and wait it will work fine. I quote "If the you get a concern of no movement in the morning or after sitting several hours, the cooler check ball should be inspected." The TSB states 2004 and prior models have the check ball in the cooler fitting. You have a 1998, so maybe that is what you saw on the net. IDK. So in essence, check ball should be in the fitting. But again, it is for a 4T65-e.