My 1992 Caravan went to the junkyard after 170000+ miles (odometer stopped working at 170231) and 14 years due to terminal rust. It just had a pan drop and filter change at 60 k and 120k with no trans problems. My 11 year old 2002 Town and Country is at 102 with no issues and I live near Buffalo NY,
Also, fluids mix, I don’t care where you introduce new fluids, the new mixes with the old. Because of its design, it is very easy to get fluid into a torque converter, getting it out is another matter.
Flushing only is better than doing nothing at all but IMO the filter change and pan cleaning is always a must.
Why should a transmission be any different from an engine oil change, a fuel pump replacement, or an A/C repair with an accumulator/drier when it comes to filters.
I’m still reminded of the service manager at one of the Ford dealers near me who stated, “We haven’t dropped a pan here in 15 years…”.
That comment is what led me to repeatedly query FOMOCO about factory policy and in typical bureaucratic fashion, they refused to commit to an answer other than “visit that Ford dealer for the finest service by technicians who have the latest factory training and equipment to properly service your vehicle”. Not.
The sales pitch used to sell those flush machines to shops pushes high profits from the “Wizard of Oz” contraption, not increased service life to customer’s transmissions. Certainly, a proper flushing would be somewhat better than a mere drain and fill but there is no pipeline pig to separate the old fluid from the new and it is likely that in most instances dropping the pan is the better alternative. My experience with fleets of vehicles indicated that dropping the pan every 30,000 miles resulted in transmissions operating 300,000+ miles. My customers were very happy with the results.
Transman is the resident transmission expert. I had my Riviera trans overhauled at 350K just because I wanted to make sure it was ok. The guys said it really wasn’t that bad and would have gone a lot longer. I had never done a flush but only pan drops and filter changes on it.