Transmission Drain Plug

[Arnold]

My '49 cub transmission drain plug won't budge. Two days of Kroil. I suspect the last time it was off was 50 years ago. Tractor has been used yearly and shed kept. The lube oil level plug screws in and out. I read here that condensation can produce water in the housing and sink to the bottom. I'm wondering if the plug might be rusted into the threads from the inside of the housing? If so, then if I do get it loose, might it then strip the threads and then I will have to tap in a large plug?
I can drain the lube oil from the top with a mightymac hand squeeze suction tool, or from the lube oil level plug.
Or, should I tap the existing square head drain plug with a smaller plug?
I've read alot of this forum and haven't found anyone who had a stuck transmission drain plug. Any thoughts?
Thanks.

[Barnyard]

Tap on the plug with a hammer and see if it will break it loose.

[Bob McCarty]

If you can clean it out well enough to use a torch, heat works wonders.

[staninlowerAL]

If the plug is a square (4 sided) plug, I suggest you look for a square socket that will fit the plug. If it is a square recessed hole look for a socket extension that will fit the hole. JMHO Stan

[Dale Finch]

If you can't get it out and are worried about water in there or the bad condition of the hydraulic oil, as a last resort, remove the PTO & Adapter Plat from the rear of the transmission/differential housing. It'll drain the fluid and you will easily be able to clean out the housing.

You can try a 9/16" female pipe plug socket, like this (you might need to grind the walls thinner to get it on the plug):

https://www.amazon.com/Sunex-2-Inch-16- ... 174&sr=8-4

You might even be able to get the plug out by drilling it from the inside with a regular right hand drill, breaking it loose and driving it out toward the front. Of course that drill bit would have to be very long to reach the plug inside the housing!

[Glen]

Hi,
Be careful to not round the flats of the plug with an open end wrench.
I don't know how long a wrench you are using, you could try a longer wrench.
The 1/2" drive, 4 sided, square socket that fits the plug is a good idea.
They make, or did make, long 1/2" drive ratchets, if you don't have one, maybe you could rent one near you somewhere.

[inairam]

I do not think "being careful not to round the plug" can be emphasized enough.

It well worth taking time to buy or borrow the square plugs sockets ( $30 fro a set on amazon https://www.amazon.com/MIXPOWER-Pieces- ... B09GKH1Y9F)

There are enough square plugs on the cub to justify this investment. Those plugs tend to be in locations that make them very hard and time-consuming to drill out and replace.

[CharlieK]

thanks inairam

[Bill V in Md]

I can drain the lube oil from the top with a mightymac hand squeeze suction tool

Or you could position the syphon hose in the lower transmission case and pump a little out to see if it is water. However, I would still continue to work on removing the drain plug.

If you can't get it out and are worried about water in there or the bad condition of the hydraulic oil

Dale, what is "the bad condition of the hydraulic oil"? Maybe you were thinking hydraulic oil in the oil pan? Thanks

[Arnold]

Thanks for all the replies. I ordered a square plug socket. And will try it with a ratchet and pipe. It's really stuck. My concern is - can condensation in the housing cause enough water to sink and rust the drain threads internally, from inside the lube oil well? I'll follow the idea of taking off the pto plate and inspect further, later this week. I definitely don't want to break the plug.

[Don McCombs]

AFTER draining, heating and using your favorite rust penetrant, you might want to consider using an impact wrench on low power setting instead of a ratchet handle and cheater.

[inairam]

Thanks for all the replies. I ordered a square plug socket. And will try it with a ratchet and pipe. It's really stuck.

remember the whole trans case is cast. The plug is steel. If you have a square socket and a lot of leverage you may crack the case. Heat and penetrating oil.

I have loosened a lot of bolts just with one of these on propane https://www.amazon.com/Intensity-Trigge ... B08LS83W94

[Arnold]

Its been awhile but here is an update. Thanks for all the helpful advise on this.

I got the 9/16" female pipe plug socket for the drain plug. I tried it on the end of an 16” long ratchet breaker rod, and on the end of a good impact wrench. No go. I siphoned out all the old lube and pulled the rear pto/transmission plate off. The inside of the plug looked clean, not rusted, and some paint removed as if it had been removed before. I kept spraying Kroil on both the outside and inside everyday for weeks. Still no budging. I tried propane torch heat on the outside and inside several times and no budging with the impact wrench, forward or backward. Thinking about the next solution I tried one more time with the long rod wrench and square socket. With not extreme muscle power it moved. I continued to use the long rod and got it off. The threads were clean and the hole was clean and didn't seem to have been misaligned. It screwed in easily and became snug. After cleaning the plug I did notice the square head had an “A” stamped into it, see photo. Does the A mean it is a plug from a different Farmall model? And with a slight thread tolerance difference?

Another curious question: I noticed the inside of the transmission is all orange. Is this typical?

[Don McCombs]

The orange coating on the inside of the transmission case is a product called Glyptal. It is used to seal the case.

[CharlieK]

another good ending