Correct Part Number for Torque Converter Drain Plug


Veteran Poster
Sep 22, 2023
Richmond, VA
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The Ford workshop manual states that after draining the torque converter, you should replace the plug with a new one.


If for argument sake I wanted to obey the manual, the stated part number is 87650S - which is obsolete.

Ford does produce  a torque converter drain plug for Mustang and Panther from 2001 onward according to my local dealership Parts guy, part number 391346S. That's odd because...wasn't it around that time that the plug was eliminated altogether?
They also didn't see anything indicating that the new part number superseded the old one.


So does anyone have a current part number? Are these two plugs in fact identical? Or do you just reuse your existing plug?
Ok, I hear you. But my skeptical nature is like: how can a little bolt with no o-ring and no kind of sealant actually seal anything?

It's a mechanical seal .. the taper on the threads creates a seal as it is tightened.

Ok, first post about NPT specifically states that it seals "with Teflon tape or jointing compound".

Teflon Tape and pipe dope are Lubricants .. they help turn the threads as they tighten.

I've installed plenty of TC drain plugs on Tbirds over the last 20 years and countless threaded connections in my career .. my journeyman card says Pipe Fitter / Steam Fitter, but I do HVAC and plumbing as well - in other words .. trust me, I do this work for a living.
Ok, copy that...

So another question: the proper torque?

In the manual it states:


Meanwhile, I saw a YouTube video where the guy flashed another manual (but still 4R70W), which stated:


Pretty huge difference!
I worked with dumbasses that put together a 20 ton press, using teflon tape on every joint. :) It leaked from every joint; hydraulic fluid extrudes the teflon out under pressure, like toothpaste. You can use it on plumbing, but npt threads are metal to metal, on purpose. If a string of teflon tape gets loose in your transmission, it will ruin it. Don't do that.if one leaks, tighten it an eighth turn more.
This is a pdf, but they are talking stainless, which galls like hell without it. We have carbon steel, it does not need tape. dope is the liquid sealant.
The trick with Teflon tape is to leave the first thread or two exposed to prevent tape from getting inside the joint and allow proper thread engagement on initial tightening. Tape always gets pushed up and out of NPT joints - it's the taper .. take the joint back apart and this will be clearly evident.

Pipe dope won't prevent a leak - in other words, it's not really a sealant. It's labeled as a sealant but that's not exactly how it works since it never fully cures.

Stainless depends on the application. Food grade or clean drinking water might use an appropriate anti-seize lubricant, or an anaerobic sealer ( these cure and harden inside the threads ) .. however, sealer won't work if the threads have oil on them - like the TC, you will never get the female threads on the drain oil free while the TC is still in the vehicle.
I've drained multiple Ford torque converters by removing that plug and I have never replaced it and never had a leak. I've never torqued the plug with a torque wrench either. I think it only has a 7/16" head on it. I think I usually just use a 1/4" drive ratchet. You don't need a 3 foot breaker bar.

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