Did some research on dryseal pipe threads (NPTF) and after reading about the design and reccomendations, I can see why the manual says to replace the converter drain plug with a new one.

Dryseal taper threads (like the ones on the drain plug)achieve their sealing ability by the interference fit between root and crest of the male/female threads. The threads are deformed when the metal-to-metal contact ocurrs.

Now this doesn't mean that you won't get a good seal upon re-assembly, but it is possible for the holding strength and sealing pressure to become compromised.

Ford states that a new plug "must" be used and though this may be just precautionary, it is recomended practice by the fastener manufacturers.

I think I'm going to go for a new plug for my first converter drain (I'll get half a dozen from the dealer, which should last for the time I plan to keep this truck).

From Parker Hannifin Corp.:

"F4
FluidConnectors
Parker Hannifin Corporation
Tube Fittings Division
Columbus, Ohio
How A Leak Free
Joint Is Achieved
NPT threads, when assembled without a sealant, leave a spiral
leak path at the crest-root junction as shown in Fig. F2. To seal
pressurized fluid, NPT threads need a suitable sealer.
NPTF threads (Dryseal), on the other hand, when assembled,
do not leave such spiral leak path. This is because they have
controlled truncation at the crest and root, ensuring metal to
metal crest-root contact prior to, or just as the male-female
thread flanks make contact as seen in Fig. F3. Upon further
tightening, the thread crests are flattened out until the flanks
also make metal to metal contact as seen in Fig. F4. Thus,
theoretically at least, there is no passage left for the fluid to
leak, provided all surfaces are flawless and dimensions exact.
In the real world, however, this is not the case and a sealant/
lubricant is necessary to achieve a leak free joint even with
NPTF threads. The sealant/lubricant fills all imperfections in
the surfaces affecting the seal and provides lubrication to ease
assembly and minimize galling."



Check out this PDF file, pages 4 through 6.

http://mdmetric.com/4300/pipe.pdf

 

Ok..OK..I'm stupid!!!!!!!

There I have admitted it. Now for the update:

Called the Ford Dealer Parts dept. and asked about the drain plug. The parts guy's answer was:

"Well, I'll have to see if I can round one up for 'ya. We don't stock 'em ... it's just a 1/8-27 NPTF pipe plug. You can pick one up yourself at Home Depot."

All I could say was: "Never mind, I'm an idiot!"

Also, if the dealer doesn't stock them, that tell's me that they probably reuse the old plugs if they have to drain the converters for service.

So.... go ahead...let me have it y'all, I deserve it! :o

 

If your really worried, use a little teflon pipe dope. That is what is used on these pipe fittings to keep them sealed. I have never used it but I may the next time.

BTW you know the drill, the only stupid question is the one not asked...

 

Be VERY careful with this! A little bit in the fluid and you can stick a valve in the valve body. Then you might have to rebuild the transmission!

 

True, but I do think it would be hard to get enough inside the torque converter....... but do take care..... I really don't think anything is needed other then the plug.....The orriginal one...

 

The clearances between the valves and valve body are measured in microns. A piece of pipe dope that you can hardly see could stick a valve.

 

This is the stuff to use for fine thread sealing on hydraulic systems. Will not contaminate the fuild and has no particles or fillers to clog valves, etc.

Loctite is the KING of thread sealers / lockers.

http://www.loctite.com/catalog/produ...++++++++++++++

This also looks applicable:

http://www.loctite.com/catalog/produ...++++++++++++++


This is just for those **** people, like me.
I've read many, many reports of people reusing the plug with no sealer and no problems whatsoever.
And I believe them! I work for a manufacturer of precision pneumatic / hydraulic operated equiment
and we always use a thread sealant on fittings, so I guess I'm just brain washed.

 

I am interested in the two very different quoted values on the torque spec for the torque converter drain plug. There's a big difference between 21-22 ft-lbs and 89 in-lbs (about 7.5 ft-lbs). Is it just a cross-over by year for the 4R70W as suggested in the thead above? Have there been any updated specifications issued over the last two years?

Heck I'm just glad that my build date is July 2001 so I still have the drain plug. Another month later and it would't even be there.