Changing automatic transmission fluid

[multipath]

I'll be coming up on the two-year mark on owning my Pro (wow, has it really been that long??), and though I won't hit the 48,000 km / 30,000 mi mark by the two year anniversary, I figure it still might be a good idea to do it based on time.

What are the benefits, if any, of going with a t-tech style service? I am VERY leary of the Jiffy Lube type places after the so many horror stories I've heard from others. I've also heard those machines can force shavings and other nice bits into valve bodies where they don't normally end up and cause problems that wouldn't have occurred otherwise.

The flip side is the "drop and drain" which really doesn't change much fluid at all.

Any comments on either, or yet some other way of changing the fluid that I haven't heard of?

[GNO]

The reason you've heard those machines can force shavings into places they don't belong is because they run a a higher pressure than what your car operates at. Some places do the "full" replacement by running the vehicle. They have the fluid drain into one container and pull from a container filled with fresh fluid. By doing so, you do expose the tranny to the high pressures, yet you get more fluid out than the standard drain and fill.

[Astral]

The reason you've heard those machines can force shavings into places they don't belong is because they run a a higher pressure than what your car operates at. Some places do the "full" replacement by running the vehicle. They have the fluid drain into one container and pull from a container filled with fresh fluid. By doing so, you do expose the tranny to the high pressures, yet you get more fluid out than the standard drain and fill.

I had my ATF changed to Synthetic Amsoil ATF at a Mazda dealer, who used a BG machine to do the total flush. Machine takes 16 qts, more than twice the actual Protege auto tranny capacity. However, because the AT fluid inside the tranny goes in many different paths, just flushing 7.6qts thru the tranny cooler lines won't get all of the old fluid out.

The machine works like this: unhook AT tranny cooler line, hook it into one end of the machine. Take other end of the machine, hook it back to the tranny cooler. The machine is like a big chamber with a diaphragm in the middle. You start the car and the tranny starts pumping fluid the way that it normally does, at normal pressure. Old fluid comes out into the machine, and pushes the new fluid out. So 16 qts of old and old/new fluid come out, 16 qts of brand new fluid come in.

There are no motors, no pressure in those machines.

Synthetic ATF rocks my world, btw. I feel like I have more low-end torque/HP (high end feels the same), and my mileage is up 2-3mpg. Where I used to get 23mpg, I now get 26. Where I used to get 26mpg, I now get 28.5. Cold shifts in the morning (kind of rough shifts) go away in 30 seconds or so, almost not there these days. I used to have those for at least a minute or two (and longer in winter). I think the synthetic ATF is going to really help in the winter.

Plus, w/ synthetic ATF, your drain interval is at least twice as long. So I don't have to worry about my ATF for 90K+ miles.