Tranny machines don't use pressure.
I've been in the oil changing business for 4 years now and I've gathered a little knowledge in that time. Transmission machines do not use pressure to flush your system. They run on the engines pressure and your engine does the actual work.
If you want to do a tranny flush on your focus (just like those big expensive looking machines), then all you have to do is get a hose for the metal end of your transmission cooler line on the radiator and attach it with a hose clamp.
All the machine does is provide a hidden bucket ( on the backside of the machine ) filled up with transmission fluid from which your car can suck it up and be "flushed".
Once you've got your hoses hooked up (and in a bucket so ur old tranny fluid can come out), get a funnel and start dumping tranny fluid in there, as you do this you'll see old nasty brown fluid coming out.
Badda bing badda boom, you've got your self a tranny flush.
Next time you go to a local oil change shop, ask to see there trans flushing machine. All it has on it is a pressure gauge and maybe a little spinning fan to show that theres flow. There is no pump, there is no loud humming noise to prove theres a pump, and oddly enough, the only reason is has a power hook up (that goes to the battery) is to turn the light on behined the little spinning fan so it can look technical.
And NO, the pressure gauge is not because theres a pump in the machine, ok? Its the cars actual pressure in the system. You'll notice on most toyotas you'll get from 5-12 psi, where as a dodge or chevrolet will give you 20-40 psi. They all vary depending on manufacturer.
In fact, the only thing you'll be missing from your do-it-yourself tranny flush is that actual gauge telling u that there is pressure. I have eyeballs for that and I can see whether or not dirty fluid is coming out.
Wanna go a little faster on your toyotas? Have a frend keep the engine a little above idle to boost the pressure in the system and boom, squirt squirt, u'r going faster!
Most cooling machines dont even have pumps (some newer designed ones do) but the only difference is that with the pump, you can do it with the car off and without the pump you must do it with the car running and the heat blowing full blast (to make sure theres heat, and no blockage to the heater core).
Just my 2 cents!, btw im new to forum and i'm going to pull my EGR valve and clean it up because the OBD2 threw a check engine (EGR EXCESSIVE FLOW). So look for my write-up (with pics) on that issue!
EDIT(to stay on topic)
And yes, if you don't flush your tranny regularly and then try to flush it down the road sometime, you can get break up clogging your tranny flow thus leading to transmission problems. Which is why most big quick lube joints (i.e. Valvoline and JiffyLube) always put on your invoice that they are NOT LIABLE FOR TRANSMISSION SERVICES OVER 60k.
Read your invoices and make sure you're not signing your cars death warrant.
