Don't forget that not only trash can come out of the converter, another troublesome source is the transmission cooler in the rad. Yes, you can try and clean that out with cold solvent, but what cleans it out the best is hot ATF, and as we all know hot ATF is a great detergent. We were a distributor for a tool called "Hot Flush" (google it to see what it is), and every customer that had one wished that they'd had one years before. Not cheap, but one high volume customer was so impressed with it he purchased a second one.