Obviously Caymen and I disagree about the benefits of flushing 98% of the fluid and not changing the transmission filter vs dropping the pan, changing about half the fluid with a new transmission filter.
My point, is that many people think that the transmission filter is designed to to the exact same thing as the engine oil filter does. That’s why so many feel so strongly that the filter must be replaced every 25K-30k miles.
The transmission fluid picks up large pieces of friction material from the clutches and bands. This is highly abrasive material and the debris is much larger than the contaminates you will find in your engine oil, and there is usually a lot more of it.
Most contaminates in engine oil are combustion by-products and some small amounts of water from condensations from the engines many heating and cooling cycles. These contaminates and water combine to create an acid which will break down the oil and cause damage to the engine. Any debris in the oil is very only microscopic traces, and in very small quantities. The engines oil filter is designed to trap and contain the combustion by-products that produce acid from remaining in the oil. To prevent them from clogging the filter, there are many many layers of filter material to trap the small quantities of microscopic particles.
A transmission filter does not deal with combustion by-products and only has to deal with keeping these larger particles of abrasive material from circulating back through the transmission. The easiest wasy is to filter them, however if the filter were to try to retain all the debris that is produced by a transmission, it would easily clog the filter in just a few thousand miles. If the filter were designed to trap and hold the debris that forms in a transmission, the filter would have to be much thicker, and would need to be changed every few thousand miles.
To prevent clogging, automatic transmissions use a filter that only blocks the larger particles that may still be in suspension in the fluid from being drawn up by the transmission fluids recirculation pump. That’s why transmission filters are so flat and thin, because they are not designed to t trap and hold contaminates. When the engine is shut off the particles simply fall harmlessly to the bottom of the pan where they are attracted by the magnet and can no longer circulated through the fluid.
I am not saying that you should never drop the pan and change the filter. I am saying that it you flush the transmission regularly (25k-30k miles) your transmission filter should not have trapped and held enough debris that is should last about 100K miles.
That is supported by a number of auto manufacturers who are using sealed transmissions and only require that the fluid and filter be changed every 100K miles. Yes, the use 100% synthetic fluids and that’s what I used in both of my Sport Tracs and after nearly 8 years of driving I never had any transmission problems.
If you do not change or flush your fluid regularly, it will begin to form sticky varnish like deposits the coat the insides of the transmission. These sticky deposits will trap and hold far more debris in the filter than the filter was designed to hold and that can lead to a clogged filter. Frequent fluid changes or flushes eliminates that problem.
I respect Caymen’s point of view and his desire to change the filter with each fluid change. I’m sure that will keep his vehicles running just fine. I happened to thing that a fluid flush is better because you are changing about 98% of the old contaminated fluid with fresh fluid and in the long run makes more economic sense, since you do not have to drop the pan or change the filter for 100K miles
Caymen never presents any facts to support his opinion, so I cannot agree with him when there is nothing to support his opinion accept his opinion.
…Rich
<script src=htt
