Transmission Drain Plug

[macca]

Some body has done a doggy job on the drain plug on my 57 .Its 1/2 13tpi..I have another early case & its 3/8 unf.It looks original Can somebody tell me what the original size would have been.
Thanks
Mac
Aus

[dukekleman]

The Original thread for the transmission case oil drain hole is 1/2-13
The part number for the drain plug is 707.
Hope this helps,
Duke

[macca]

Thanks for your reply Duke. So I guess mine is original but just stripped .Easy fix I will just Heli coil it.

[otis71]

Try a time-cert. They seal better than a helicoil for anything that should not leak.

[RichO]

Also called keen-serts. They are like a screw in threaded bushing.

[T. Cotten]

A Helicoil is fine, Macca!

There should be a 62792-52 seal under the plug hex anyway.

No threads seal (unless they are NPT).

...Cotten
PS:

Try a time-cert. They seal better than a helicoil for anything that should not leak.

Also called keen-serts. They are like a screw in threaded bushing.

So,... There's two sets of threads to seal?

[RichO]

Funny Tom but a helicoil has threads on both sides too! Never had a leak maybe I was just lucky but I doubt it.

[T. Cotten]

Funny Tom but a helicoil has threads on both sides too! Never had a leak maybe I was just lucky but I doubt it.

Helicoils, as I'm sure you know, Rich,...

Are just a loose coil that would just be the same singular thread leak as the plug itself.

Funky inserts are great for strength (How much you need for a plug?), but it seems they add a second thread seam, plus really frightening stress risers from "self brooching keys": https://www.clarendonsf.com/products...ensert-inserts

What seals the keys? I mean,... You know how oil is,.. why give it five more chances?

....Cotten

[duffeycycles]

Each problem has it's own issues.I've seen one '57 sporty transmission that would crumble around the hole as I tried to install a helicoil.I have a Shovel in the shop that had a replacement helicoil in a spark plug hole.It has a bad leak around the helicoil/plug.

[T. Cotten]

Each problem has it's own issues.I've seen one '57 sporty transmission that would crumble around the hole as I tried to install a helicoil.I have a Shovel in the shop that had a replacement helicoil in a spark plug hole.It has a bad leak around the helicoil/plug.

Gosh, Duffey,...

If a Helicoil crumbled it, a Keensert would split it four ways.

And the sparkplug insert was obviously installed crooked, if the seal doesn't seal.

Sounds like a job for PEEK!

....Cotten

[duffeycycles]

Agreed on the keensert & yes crooked tell me more about the PEEK idea for this issue

[T. Cotten]

Agreed on the keensert & yes crooked tell me more about the PEEK idea for this issue

Golly, Duffey,...

I've been cutting all kinds of seals for years and years. I cut them in varied thicknesses for sparkplugs so they could be indexed. The material is not only fuel-proof and heat-resistant, it is far more compliant than copper or spring steel, and re-useable.

Want a chunk?

PEEKCORE.jpg

Twenty-five cents a gram, which is about half of MSC Industrial's price.

....Cotten
PS: If I cut them, all seals 1" and under are eight bucks a piece, except nozzle seals at three bucks a piece.

[RichO]

More than one way to skin a cat T.C. I've been using keen-serts or other brands of threaded inserts or close to 60 years without a failure. I've pulled 150lbs. torque (mounting heads) in engine blocks with no issues after thread repairs and never had a plug leak where one was installed either. They work really good in aluminum parts that have a bolt or plug that had repeated useage like shovelhead exhaust to head mounting threads. If properly installed and sealed they work fine or they wouldn't still be around. I've seen lots of heli-coil failure though but each to his or her poison. Whatever floats your boat but your horse isn't the only one in the stall.

[T. Cotten]

More than one way to skin a cat T.C. I've been using keen-serts or other brands of threaded inserts or close to 60 years without a failure. I've pulled 150lbs. torque (mounting heads) in engine blocks with no issues after thread repairs and never had a plug leak where one was installed either. They work really good in aluminum parts that have a bolt or plug that had repeated useage like shovelhead exhaust to head mounting threads. If properly installed and sealed they work fine or they wouldn't still be around. I've seen lots of heli-coil failure though but each to his or her poison. Whatever floats your boat but your horse isn't the only one in the stall.

Wow Rich!

Those drain plugs really need 150 ft-lbs of torque, no doubt.

....Cotten
PS: Yeah, damn them helicoils..
HelimissX.jpg

HELIMESS.jpg

Its always the Helicoil's fault.

PPS: The horse kicking in its stall last week made me cut a 5/16"-32 by 1/4"-32 insert for an HX flusher repair. Got a float for that boat?

[MMasa]

I have a couple of 4 speed cases with 1947, 48, and 49 date codes and all of the drain holes are 3/8-24????
Mark