I have a Merc-o-matic behind a 312 in a 1956 Mercury. Both engine and trans were rebuilt recently, however there have been enough issues since to keep me from returning to that mechanic. The latest to surface is a leaky torque converter. It's probably always had an occasional drip but it is fairly consistent now. It leaks even when the car is not running.
I've removed the inspection plates and air duct to have a good look. If I wipe everything dry and come back next day, the fins are wet. The cover plate is always dry and the transmission is dry.
So it seems to me that the fluid must be leaking down the back of the torque converter and then dripping off the fins. And if that is the case, what is likely to be wrong? A seal of some sort I imagine.
I have not removed this before, so I guess I will need to pull the trans, bell housing, torque converter together and then remove the torque converter on the bench to replace the seal?

thats right theres a seal you can get a macs and the t bird site to replace it easy job ive done a couple.pulling everything apart is the big job.

When you get it apart, check the fit of the converter hub in the front pump.  There should be minimum play.  If it is loose, you will need to replace the front pump bushing.  That will require taking the pump off (4 bolts) and taking it apart (1 or 2screws) to  replace the bushing.  A loose bushing will likely cause the seal to leak.  Parts should be available at your local parts store.  Good luck.

John - "The Hoosier Hurricane"

good advise  from hoosler,while you have  trans out check the drive tabs  that come loose allowing torqe.  converter to flop around which wears the  front pump bearing..    always  reinstall trans and torqe assembled  so as  not damaging pump drive tangs.

Can anyone point to the right parts/numbers for the seal and bush? And particularly where they might be available in Australia?

may have to purchase a new front pump assembly. I would go that way as installing bushing and seal risky if you have not don this be for

http://www.autotran.us/fmkits1.html

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EXCELENT INFO.

I got the trans and converter out today and the photos show the story maybe. The first photo is the seal - not much to see I guess, but it will need to be replaced.

The second photo maybe shows the culprit. Is this the bushing that Hoosier mentions? I can't get excited about the rough finish and I reckon that lip is about where the seal sits. So I hope replacements are available.

That stub on the converter is what rides on the front pump bushing and the seal.  That hub that bolts into the converter is also sealed with a seal similar to an O ring but has a square cross section.  Unbolt the hub to see the seal.  Where the converter halves bolt together is also sealed with a square cross section "O ring"..  Any of these seals could cause a leak in the converter area.

John - "The Hoosier Hurricane"