The transmission on my 2000 f150 4.2 seems to have a heavy whining or turbine sound when I'm on the gas and the rpms are up a bit - hot or cold. When lightly and quietly cruising around 35 mph then pulling the transmission into 2nd gear (testing)- it whines pretty darn loud so it seems to be high rpm related as well as torque. I think it's always had a bit of a whine but this seems quite noticeable now. Apparently the torque converter was replaced by the dealer before I bought the truck. Mercon 5 fluid changed about 4 months ago and is in good shape and correct level. The whining changes tone with rpm and the tone goes up and down with rpms and gear changes. When rpms are around 2000 or less with light gas it's fine in any gear, it seems to be most noticeable when there is torque required like merging into traffic from a stop. Shifting is fine except if you're really on it and it jumps down into first, then when you let off the gas a bit, it takes forever to shift up. Do others with the 4R70W notice a loud whine at times or have I got transmission troubles coming? Should I try an additive? Should I take it in for the dreaded transmission check $$ or does this seem fairly close to normal?
Thanks for any advice !!!