I've never tried the kick-down switch, don't even know if it works!

My 87 300D has 251K. With the shift lever, I generally drop down one notch, from 4th into third, at around 30 mph sometimes when encountering a steep incline.

Last year, I voluntarily added TRANS-X to the tranny because others here spoke highly for it. I did so because it is supposed to remove the sticky film that supposedly builds up on internal valves and other moving parts that can stick stuck. Also it conditions seals, but I've always been a little leery about chemicals that cause rubber/synthetic seals to marginally expand in size?

I have also switched to synthetic tranny fluid. Later, somewhere I heard that this is not good to do with an older tranny, but you can't believe everything you hear, but if anyone knows more about this, please elaborate!