Originally Posted by SPOILEDRED94
I have often wondered why the trans pan has no drain plug. The pan is like an 1/8 in thick. Good for drilling not for threading. What do I do..? Weld the nut to the inside of my drilled hole?
Here are three reasons I can think of: First, it would cost GM another $0.20 to provide one that could otherwise go to profit. Second, for most folks who service the transmission at the factory recommended intervals, by the time you remove the pan, there are a lot of particles that have built up there. The only way you can get those out and prevent some of them from being re-circulated is to drop and clean the pan and the magnet. Third, you need to drop the pan to change the filter.
If you were going to do a pan drain plug, you might consider welding or brazing a fine thread nut to the rear vertical outside surface of the pan, perhaps in one corner or the other. You could locate that much closer to the bottom of the pan (to leave fewer dregs in the pan) without exposing the nut to accidental damage/removal if the pan scraped over an object. Corner placement would allow you to jack one front corner just a bit higher than the other to encourage even more complete draining.
Where it would be really nice to have a drain plug is on the torque converter. Some cars do have these as well as a drain plug in the pan. In that case, an access opening is provided in the bottom of the bell housing allowing a fluid change to renew almost all of the fluid. If you were installing these on your own, you would probably need to do two or three of them to ensure the balance of the TC was not compromised.