And I'm simply asking if you are willing to do the same with engine oil. Basically the same type of system. There is a filter and a way to change both because they wear and the additives break down. ;)

Not to beat this thing to death, but I'm going to have to repeat my question to you. Do you believe that the flush truly caused the failure or did it merely expose an already failing/weak transmission.

Second, the "proof" you have is a friend who's transmission failed after he flushed it. You do know that there is a right and wrong method to flushing the transmission, right? Like anything else done incorrectly, a trans flush done wrong can cause damage. That does NOT mean, however that flushing itself causes damage.

For your proof, was a diagnostic breakdown done on the failed transmission? What did they find to be the actual failure mode? How did that relate to the trans flush?

Now, before you get mad at me, understand that I'm not trying to pick a fight or prove you wrong or anything. It's more important to me that we make sure that we, as a club, do not pass on mis-information if we can possibly avoid it.

An educational thing I did, was to spend some time researching the subject, both on the web and through some good old-fashioned reading. I encourage anyone to do the same. More information is better than just a little.

So, in the interest of presenting both sides..

There have been rare cases where a transmission flush has been determined to have "caused" a trans failure. Those incidents were attributed to one of two causes

1) Seasoned mechanics will often refuse to flush a trans that has severely burnt fluid or that has never been flushed or had a filter change with many miles on the vehicle (100,000 plus). The given reasons are twofold.

A. Severely burnt or dark brown fluid is no longer doing its job. The additives are not cleansing the system and there is likely already damage. A flush in this case could dislodge large damage particles that move and then do further damage. This transmission was going to fail anyway, but it's demise was hastened.

B. Many of the valves and passages in your trans have very small passages in them. A transmission with many miles on it that has never been flushed will have "collections" of deposited wear particles that have settled in lower flow areas (there is a magnet in your trans pan that is designed to catch the normal wear particles, but excess will find it's way elsewhere). These sediment areas can break off in chunks and lodge in a small passage, causing fluid blockage and possible damage.

2) Apparently, there are shops that lazily don't do a transmission flush correctly or do not use the correct equipment. In this case the actual flush can damage seals, according to some articles I read. This is NOT the case for shops that use modern equipment and trained techs, though. This item is the one I read the least about and I did not research it any further to understand completely why this occured.

The bottom line is that both Manufacturers and Dealers include regular flushes and or filter and lube changes as part of regular maintenance.