This one is going to sound weird, but -- My 400E with 120,000 miles starting acting up as far as the transmission. It began to hang in lower gears and sometimes downshift prematurely. I checked the tranny fluid and it was low (very low). Strange thing is - no evidence of leakage. I have since had to add fluid every couple of weeks. I have also noticed a slight puff of smoke from the exhaust. No engine oil usage whatsoever! Does this model use a vacuum modulator on the tranny and could it be leaking fluid into the intake of the engine??? Thanks Dave