Gearbox drain plug leaks

[osprey877]

The drain plug on my Hurth gearbox does not seal properly and drips ATF. Not a big leak, maybe a thimblefull every couple of hours. Annoying and messy.

The problem is the threads in the aluminum case are partially stripped and as a result I cannot properly tighten the plug. The permanent solution is to drill and insert a helicoil. However, there is no room under the gearbox to drill and I don't want to pull the gearbox.
I have tried doubling the copper crush washers, using garden hose rubber washers, rubber O rings, teflon tape, plumbers putty etc. but the leak persists. I am thinking now I will try some sort of silicone or gasket goo. The gearbox uses ATF and although it gets hot, it is not under any pressure so it shouldn't be too hard to seal. I could even go to a semi-permanent seal as I could always drain it by pumping out through the filler plug rather than draining out through the drain plug.
Anybody have any suggestions?

[Jammer]

Self-tapping, oversize drain plugs are available from Dorman to fit most housings.

[osprey877]

Thanks. I will check out Dorman's website and hopefully they will have something that will work.

[Pepijn]

Osprey, what was your solution? Did you go for Dorman or a different solution?

[osprey877]

Originally Posted by Pepijn

Osprey, what was your solution? Did you go for Dorman or a different solution?

I ended up permanently epoxying (JB weld) the plug in place. Stopped the leaks, but meant I have to pump the gear oil out of the top plug to do an oil change. There is probably a way to put some sort of lubricant on the plug threads before you cover them with epoxy and screw it into the gearbox so that you can still remove the plug once it hardens. Or maybe remove the plug when the epoxy is 90% set. I didn’t do this though and mine is permanent, although I suspect I could probably force it out with a large wrench if I had to. Good luck.

[Pepijn]

Thanks for your reply. We did 4 turns of teflon tape and a bead of butyl tape below the head of the bolt. So far so good after 24 hours. However, if it starts again we will consider a more permanent solution as you did. As you point out the oil can be extracted from the top as well. Thanks.