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CinneaghTR
02-12-2010, 05:49 PM
Do you guys know the thread pitch for the TRactor oil drain plug? Part #114774 It is the same for the heater line fitting coming out of the water pump housing. I am looking for a tap so I can clean the threads.

https://www.revingtontr.com/shop/product_...roductID=114774 (https://www.revingtontr.com/shop/product_display.asp?mscssid=DF7QAJL3J9LW9KDPW2X6EA 6LKJDKCVQ5&CarType=TR4A&ProductID=114774)

Revington TR cross references a 5/8 UNF drain plug (103222)? Could that be it? I just need confirmation because the last thing I need is MORE stripped threads. Don't ask...

Thanks in advance.

PeterK
02-12-2010, 05:58 PM
3/8" NPT. It uses a tapered pipe thread.

MGTF1250Dave
02-12-2010, 06:49 PM
Aloha,

You can get 3/8" NPT plug is a variety of material (brass, iron, etc.) at most hardware or home improvement mega-marts. A pipe supply store might even have them with hex heads. I used epoxy to glue a small magnet in the plug and seems to work fine. I recently changed the oil in the rear end and the magnet was still firmly in the plug. As Peter recommended use Teflon tap to assure a seal and make removing the plug easier years from now.

TR3driver
02-12-2010, 06:55 PM
That's correct for 114774, although earlier cars used a different plug (V.7535).

The plug is just a standard pipe plug as well. Unless originality is important to you, I recommend switching to a magnetic, socket-head pipe plug.
https://www.mcmaster.com/#1072a22/=5shnjo

These are much less apt to round off, and seal better; plus of course the magnet helps catch and hold any loose metal fragments. You'll need the matching wrench too, of course
https://i258.photobucket.com/albums/hh260/TR3driver/Stag%20diff/DSCF0025.jpg

I also recommend the use of either Teflon pipe 'dope'
https://www.mcmaster.com/#5477k13/=5shpfl
or Loctite 567
https://www.mcmaster.com/#45855k14/=5shqfz
on the threads.

Although some folks use the more common Teflon "tape", I don't like it because strings of it sometimes get loose inside, and block passages.

CinneaghTR
02-12-2010, 11:14 PM
Thanks, guys. 3/8"-18 NPTF it is. I've got a crusty old water pump housing and I want to make sure the threads are nice and clean for the new heater pipe fitting.

I've got one of those magnetic oil drain plugs that I was planning to put in after installing the new oil pan gasket sometime this year.

I bought a roll of teflon thread sealing tape last time I was at NAPA, but I will look into the liquid variety.

CinneaghTR
02-12-2010, 11:33 PM
Man, I hate to ask you guys these basic questions. Should I be ordering a NPTF or NPT tap? NPTF is dry seal and NPT requires a sealant. MMC has different part numbers for each.

NPTF
https://www.mcmaster.com/#2525a215/=5slc49

NPT
https://www.mcmaster.com/#2525a174/=5slcg0

TR3driver
02-13-2010, 12:21 AM
If you are going to spend that much on a tap, I'd probably go for the NPTF version. NPTF is only a slight modification from NPT, designed to provide better sealing.

But I have just a cheap carbon steel tap, similar to https://www.mcmaster.com/#2525a114/=5slxnh and it works fine for chasing threads and the occasional hand tapping job. HSS is for machine tools that can build enough heat to soften the edge of carbon steel; but a hand tap shouldn't be turned that fast anyway.

poolboy
02-13-2010, 11:18 AM
The 3/8 -18 NPT taps are usually common in the plumbing department of local hardware and big box building supply stores for less than 10 bucks around here.

PeterK
02-13-2010, 01:31 PM
I agree on the teflon tape. I wouldn't ever recommend using tape on any threads that go into the engine (or any other mechanics, like gearbox or diff.) Same recommendation on using silicone sealer on engine parts. Excess strings of either stuff can get into small places and clog stuff.

Use pipe dope (teflon in a tube) on pipe threads instead. Tapered threads are really the only application for sealant.