I have only flushed my tranny's at Jiffy Lube. I have never had an issue. The reason I went with the flush instead of just dropping the pan and changing the filter is you actually get a more complete fluid change. I do understand not wanting to push the junk from the bottom of the pan into the tranny and it's cooler. If there was a way to get a more complete fluid change with just dropping the pan I would go that way.