How you drive doesn't have that much to do with how long the transmission will last. I have 241,000 miles on my '88 Grand Caravan and I regularly drag around a tandem axle enclosed trailer that's bigger than that van, and the fluid and filter has been changed once in the life of the van, only because the $3.50 side cover rusted out so I had it apart anyway.
The fluid and filter change was always the standard procedure at every 36,000 miles or three years. There never was such a thing as a transmission flush machine until we started running into trouble with computer-controlled transmissions in the '90s. A lot of that was due to the parts being made lighter and cheaper for better fuel mileage and to save money. Flushes don't fix cheap.
We have all heard the stories about transmissions failing shortly after they were flushed. The thought is debris is washed out and circulates around, then chews up the seals it gets caught in. There's a lot of arguments against that. First of all, flush machines push fluid around the same places the transmission's pump does so if anything was going to be dislodged, that would have happened a long time ago. Next, that debris would get stuck in the filter. One guy I worked with who was teaching transmissions even went so far as to believe the "grit" that makes up the fiber clutch plates had broken off the plates and was circulating with the fluid, and it was needed to keep the clutches from slipping. If you drained it out you would have slipping problems after that. He didn't have an answer as to why that grit didn't chew up the seals, and why, if that material had flaked off the plates how they could grab at all.
My thought is not many people get their transmissions flushed for general maintenance. They show up all of a sudden after they notice some problem developing, then think the flush is going to cure everything. In reality, by the time there are symptoms the damage or wear has taken place and new fluid isn't going to help.
My suggestion is if you aren't having a problem, have the fluid and filter replaced again in another 36,000 miles, or whatever is recommended in the owner's manual. Engine oil is changed much more often because the additives wear out and there are combustion byproducts that settle in it and form sludge. We don't have that trouble with transmission fluid.
If you do develop a transmission problem it is not going to be due to not having it flushed. It is going to be due to high mileage and normal wear.
Saturday, May 4th, 2013 AT 3:23 PM