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Transmission Article - Adding a Transmission Drain plug

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Adding a Transmission Drain Plug

When you have the pan off you may want to install a drain plug in it.

Parts needed:  

1 M12 x 1.25 x 30mm drain plug

1 M12 x 1.25 nut

1 12mm ID plastic washer

Paint (your choice type and color)

Tools needed:


Center punch

Drill motor

½” drill bit

Torque wrench 0-75 FT-LB or 0-300 IN-LB 

Socket to fit drain plug


An automotive supply store like NAPA will have the M12 x 1.25 x 30mm drain plug, nut, and plastic washer.  Using a strong (rare earth) magnet on the outside of the pan to hold the nut in place, you can find the area where the drain plug will clear the valve body and a large surface area for flat contact with the sealing washer.   The left front corner of the pan has the most clearance.  Center punch the spot you want to drill.


Drill a 1/2" hole then place the bolt through the hole and thread the nut to it from inside the pan.  This will center the nut over the hole.  Tack weld the nut to the inside of the pan over the hole in three spots.  The three weld spots are done so not to warp the pan and to allow fluid to be able to drain under the nut.   After the pan cools clean the outside of the pan and paint to stop rusting.  Install the drain plug with plastic washer and tighten no more than 20 FT-LB (240 IN-LB).


You may want to have a dedicated 12 quart oil drain container for the ATF.  If you have to make adjustments inside the transmission (e.g., replacing solenoids, adjusting line pressure) you can drain the ATF into the container and reuse the fluid if it is still good.



Left front corner inside of pan



Left front corner outside of pan

There are no warranties implied or expressed

Written by:

J. Daniel Martin

AKA IBMobile



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