I have a magnetic oil pan heater I stick to the drain plug, remove before dumping oil so oil flow will help metal shavings come out in the drain process. If it works or not I do not know but like someone else said, It makes me feel good.

 

Good idea, but I don't think the "mud" will just flow out. Most tranny pans have a magnet in them also. The only want to clean it is to drop the pan. I realize the magnet is on the outside, but the mud is not going to just "let go" and flow out if the magnet is removed.