Rear Diff Plug HELP

Diastole

Diastole

Senior Member
I am new to Model As. I have a early '30 coupe.

I want to change the diff fluid. This car sat in a garage since 2015.
Owner recently passed, sadly. Rest his soul.

The fill-drain-plug has half of the lugs sheared off. I am looking for some help for a possible solution on how to remove it w/o damaging the housing.

See photos

I can try some vice-grips after heating the metal housing. Or, drill a hole, tap with left hand threads, and install a left hand thread bolt. Or weld a 3/8" square bar in what remains of the plug.

Being Model A's are new to me, and my interest to not reinvent the wheel, I am asking for any help or suggestions I can get.

I can do two of the three thoughts above, I do not have left hand tap and die set.

Thanks in advance

Diastole in the Smoky Mountains
 

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If it was mine I would weld a large nut to it , should come out easy, sometimes easy outs makes a easy job hard
 
Try the vice grip first. I would avoid drilling the plug because of introducing chips into the housing. If the vice grips fail, I would grind off what is left and then weld a nut onto the plug, as Randall said. Do the weld in steps so as to not heat the housing too much. The heat from the welding should help with the removing the plug.

My plug on my differential has the square hole recessed in the plug and is a much stronger design. Buy a new plug from one of the usual vendors.
 
I vote no on easy outs, if they break, the job gets 10X worse. If you can weld, go that way. Chase the threads with grease in the flutes of the tap to keep chips out of the diff. I use Teflon tape on my plugs.
 
Bruce, I will second the use of Teflon tape. Not only will it seal but it will prevent the plug from freezing in the housing.
 
Wire brush, and penetrating oil sprayed liberally on it 3 x day for at least a week first. If you own a Model-A now you need patience!

And I do not mean WD-40!
 
I would take it to someone that knows how to weld and have them get it out someone like a professional welder or a body shop that has the tools to remove it or a Ford dealer would have the tools to remove the plug as there are places that work on just Model A's around have them get it out for you as you mass that up you will never get it out.
 
If you chase the treads as Bruce suggested in Post #6, flush the case with a solvent like kerosene and, in any case, add a magnetic plug at the bottom as Blockhead recommended in Post #8.
 
Heat the plug , Don’t heat the housing! After the vice grips don’t work, try a center punch tapping it in a circular motion in counter clockwise. For those suggesting welding a nut ? Don’t you first weld a washer and then a nut to the washer ?? When I worked in an airline tire and wheel shop sometimes to remove counter sunk screws we would have a welder tig weld 2 towering **** to the screw heads and then used vice grips.
 
Charlie, not enough sticking out for a pipe wrench.
Gene, started applying Kroll penetrating oil yesterday. Would you prefer PB Blaster?
Group, if I am going to weld a bolt, I do not want to screw up the two sides sitting proud. If I going to weld a nut, it does not matter. So vice-grips option is still pending. The nut likely has not been removed in 19 years in talking to the widow wife. Husband complained about that after they bought it 2005.

I like the welding idea yall propose. I'm a savy novice welder. I went to the mill and bought a piece of 1/2" square bar. It matches the 1/2" socket designed for the plug. I can weld that to the raised edges and use a 1/2" wrench. Once the penetrating oil soaks in.

I ordered 1/16" welding rods with flux since I am out of gas for the MIG welder. That should give me plenty of penetration. I do not have a TIG peddle.

Bob, thanks for the IM. I agree with your diagnosis. The problem is the damaged plug has a 1/2" recess for a socket wrench. That leaves very little metal of the plug to accept the torque. The new plugs have a 3/8" recess and that leaves more metal on the edge. See photos. I will replace the drain plug with a magnetic one and thicker walls, thanks, nkaminar.

Plan to try on Wednesday (four days hence). I will update you'all.

Thanks,

Diastole in the Smoky Mountains
 

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Yeah, thats the plug I have. I bought a 3/8 breaker bar for it that just fits my plug.

Your idea of welding in a square shank is excellent.

Love, love, love the Smoky Mountains. You are so lucky to live there. How about sharing some photos of where you live.
 
I'm a gas welder myself. I braze cast iron like that so that the banjo casting doesn't crack. It would heat the plug in the bore well enough for it to come loose. Heating and welding cast iron can be tricky. Concentrate heat on the plug as best you can. Let it cool slowly.
 
Kroil is great!

Don't chase those threads with a tap. Pipe threads are not that way, ask a machinist.

If you go the weld a nut on, turn the air on an impact gun down to 30lbs, and hit it a time or two with the trigger. Advance the air 5lbs each time. It will come out.

Wait ill you get a gas bottle refill...you will be glad you did.
 
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I think a gentle hand with a pipe tap would be okay to straighten out the threads, especially at the entrance. It is different from running a machine thread tap or chaser through a tapped hole.
 
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