RandalPark@xxxxxxx wrote: "I just don't see how changing the fluid could hurt the unit." I'm not saying I agree with the following, but years ago, a mechanic mentioned to me that if ATF is not changed at the proper intervals, the fluid will eventually start to go bad and will begin to leave deposits on the various surfaces within the transmission. If the fluid is then changed, the fresh fluid will start to clean these deposits from the internal surfaces. These freed deposits supposedly can clog the valve body and get trapped in various other parts, affecting transmission performance. He likened it to adding fresh gasoline to a fuel tank that had evaporated and sat for many years. The fresh gasoline loosens the deposits within the fuel tank and they can clog the fuel line, fuel pump, carburetor, etc. Again, I'm not saying this is factual, nor that I believe it, but this was his theory on how changing ATF can suddenly affect transmission operation. K.