Inspection of a 904 torqueflite

glhx said
You used round stock and the welder just filled in the base and built it out?

Did you drill all the way through 1/8 npt. My biggest problem was the angle on this and the plug just threaded all the way through the hole because it had nothing to seat against.

I was thinking maybe do a 1/4” diameter all the way through to the valve body......and then drill a size or two bigger for the plug....just not going very deep with it. Maybe 3/4” deep or less into the long drilled hole. so the plug would seat. Using a 1/8 pipe thread which has an outside diameter of closer to 1/2” (.40). It looks like that’s what you did and a&a did as well.

Your plug is sitting flush with the surface.

What would it take to trash the case to the point it’s ruined in this particular area?

I looked at 3/4 x 1” bar stock 6061 aluminum on eBay to start with, but I’m not around the transmission right now. Just looking at the pictures. The welder might even have this bar stock laying around and have an idea of what they want to do.

Well judging from your terminology, you do understand that all pipe plugs are tapered. You cannot just drill all the way through with 1/8 pipe. No such thing. There is a specific tap drill size that you drill all the way through with and then you thread the hole with the 1/8 27 pipe tap to about half the taps length. I do not think you have ruined your case. The key to doing this job is to fit the bung to the case so there is very little gaps anywhere. This will make it easier for the welder. We kept damp rags around the pan rail to keep the heat down and avoid warpage.
As I said earlier, hand files are your friend. A welder/fabricator may be able to supply the aluminum and do the whole job for you.
Some people just buy the race prepped case from a and a that comes with the external adjustment and many other features already done. My threaded hole actually has to plugs in there one on top of the other because I went too deep with the tap. My bad.
My bung started as a piece of round bar stock. I then filed ground on a bench grinder one end of it to get the shape of the case.
When it is square and pretty well gapless on the case, have it welded on. Once welded I filed everything to get the pan rail smooth.
After that you have a flat surface to locate and drill a hole right through and then thread the hole.