There are several subjects that tend to be a never-ending source of confusion to customers of replacement transmissions. One that constantly comes up is changing or flushing the transmission fluid in the Toyota truck transmission. As usual most of the people that are confused and causing the confusion are Certified transmission Technicians and service reps.
I have learned a lot about the transmissions over the years and Toyota transmissions specifically. The first unit of this nature was one of the units in the 96 4Runner, and would like to share what I know and I hope it cuts down on some of the confusion.
The transmission on the 4Runner/Tacoma is not made by Toyota. It is a nice, high quality unit that is used by several vehicle manufacturers including Jeep. The A/W 340F model transmission to be exact.
I have seen the inside of many transmissions while it was torn down to full dissassembly having its upgrades installed during a rebuild. When it was reinstalled in my truck with its new torque converter, initially we put in 8 quarts of fluid and brought it up to 13 quarts before road testing. When we returned from the road test the we put another 2 quarts in to bring up to the full mark. Now if you were counting that is a total of 15 quarts of fluid.
If you decide to change the fluid like you should, you cannot get all the fluid out by draining the pan. When you drain the pan through the drain plug you will only drain about 5 of the 15 total quarts. That is not much of a fluid change at all. Most of the fluid is inside the torque converter, transmission cooler and the cooler lines. Some vehicles like Mercedes have a drain plug on the torque converter so it can be drained, but not on our Toyotas. There is only one way to get all the fluid out of the transmission so you can replace it with new fluid. That is to flush it.
There seems to be as much bad info out there about transmission flushes as there is about synthetic transmission fluid. The number of professional mechanics that claim that a flush will blow out the seals and cause damage to the transmission dumbfounds me. Those poor people are suffering from terminal ignorance and refuse to understand the benefit of a proper transmission flush.
Here is the BIG secret about transmission flush machines. They do not use pressure at all. They use the transmissions own pump to move in the new fluid that displaces the old fluid and the old fluid is collected and thrown away. There are two basic types of flush machines and here is how they work and the differences in the two.
Which is another article in itself. I hope you see the difference, simply put, if the pan is not lowered and the filter is not changed, it is not a real transmission flush/service. A false flush builds unreal expectations on how long your transmission may last, making it a bad investment.
Use your new knowledge on flushing machines when you ask for a flush, accept no less. Good luck and enjoy.
