Slipping at constant speed

mercury
sable

#1

2003 Mercury Sable Wagon, 120,000 miles, mostly highway. While maintaining a constant highway speed, every once in a while the transmission feels like it slips. This only lasts for a second or two. Transmission fluid just changes at 100,000 miles/6 mos ago. Does anyone have any suggestions as to what I should start looking for to diagnose?


#2

Was that the first change? the one at 100,000 miles?


#3

What’s the tachometer doing when this happens? Does it go up? If not, it may be a slight engine misfire and not a transmission problem. Did you change your plugs at 100K miles?


#4

Sorry, first change was at 50,000


#5

I did not notice any change, will have to pay more attention. Yes, plugs were changed at 100,000 miles