Quote Originally Posted by SyntheticShield View Post
If you think about it, there is little difference between having the transmission flushed and doing a pan drop. If you do a pan drop and change the filter out and then flush it, there is no difference between the two.

A transmission shop simply hooks up a machine to the transmission lines and uses the transmissions own fluid pump to exchange the old fluid for new fluid. Even if the shop did not drop the pan, felt type filters (like the ones in our car) cant be back flushed. I had a hard time visualizing this until I pulled my own filter apart and its a two piece filter felt element that are sandwiched together. So debris gets trapped between the two pieces of felt and wont go back into the system.

Older screen type filters you could back flush because it was as its name implies, just a tight mesh screen. Debris got trapped on one side of it as opposed to in between the layers like the felt filters.
The shop that replaced my tranny said the issue with the flush is the old fluid is removed and the new clean fuid is put in. It cleans the varnish and causes things to loosen that have seated over time. Then you end up with slippage and then failure. He said newer fluids have mild detergents and if you havent flushed regularily then its bad. 70K or so and its a first flush, not a good idea. I dont know how true this is, all I now is our trannys are expensive. 3 FWD cars later, a boatload of miles, 276k, 170k, and 130k, no flushes ,no issues Thats been my experience. Like I said I am by no means an expert, just my experience with it.