View Full Version : TR4/4A TR4A Transmission Overdrive Plug Leak

05-22-2011, 12:11 PM
That big fat brass notched plug seems to be leaking. I tried a new fiber gasket and it's just as bad.

Should I have used teflon tape on the short threads?

Can I reuse that fiber gasket if I remove it?

How tight do I need to get that plug. I don't want to harm the tranny fitting.

Just as importantly, should I be looking for other areas of leaking--it seems wet just a little bit above that plug.

Finally, is there a necessary tool for that plug or can I use a brass drift and tap it around? It's a bit tricky that way.

Thanks all.

05-22-2011, 03:33 PM
I just changed my OD tranny fluid two weekends ago to Redline MT90. So far, extremely happy. The SAE30 non-detergent motor oil I was using gave a notchy third gear - especially when hot. MT90 has made this the best transmission I have ever driven, period. The MT90 is comparable to a 75W90 gear oil and I believe it spins the synchros better for smoother shifting.

Anyway, I used just a light smear of Permatex Form-A-Gasket 1A on both sides of the washer. Installed the brass cap and washer. Allowed it to dry 24 hours before filling tranny.

Interestingly enough, the Moss catalog states the fiber washer on the brass plug applies to all EXCEPT the OD tranny fitted to the TR4A IRS. Not sure what that's about but, a fiber washer came off mine and I installed a new one (the new gasket was noticeably thicker than the old). And when I filled it with the SAE30 oil 3 years ago I re-used the original fiber washer with no issues. Same gasket sealer.

As for removing and installing the brass plug, I used a short 2x4 piece of wood, caught it on the edge of one of the brass tabs and tapped it several times before it moved. Then used a strap wrench (used on oil filters) to unscrew the remaining way. Same for installation.


05-22-2011, 03:35 PM
BTW, the "new" fiber washer I installed was not the smoothest in the world. I went on the faith that a) the Form-A-Gasket would fill-in the imperfections and b) the fiber washer would crush under the torque of the brass cap.


05-22-2011, 03:54 PM
Someone on eBay sells a tool to remove the overdrive filter cap if you want to spend $58 versus using a brass drift (which is what I used as well).

eBay Overdrive Filter Cap Tool (https://cgi.ebay.com/ebaymotors/TRIUMPH-TR2-TR3-TR4-OVERDRIVE-TOOL-/140497768550?pt=Motors_Automotive_Tools&hash=item2 0b651d066)


05-22-2011, 04:56 PM
If you've been using a drift on the plug, chances are very good that you have distorted the sealing surface. You might be able to file it back flat.

Here's a simple tool I made in about 20 minutes:

05-22-2011, 05:15 PM
And a fancier one where I bought a big socket on eBay (about $10 IIRC) and milled some teeth into it.

05-22-2011, 05:17 PM
Teflon tape won't help (it's only for tapered pipe threads and these threads aren't tapered). But your favorite gasket dressing (I use Hylomar) will, along with making sure that both surfaces are flat.

05-22-2011, 05:18 PM
See that guys, Randall's in business.
Anybody need an overdrive tool?

05-22-2011, 08:42 PM

I'd buy one. :smile:


05-22-2011, 08:50 PM
Sorry, not for sale. Just trying to present some alternatives.

05-22-2011, 10:08 PM
I could try making that tool.

Those bolts are filed flat so they fit tight in each notch, correct?

And you turn the steel plank (or plate) by hand, or just tap that with a hammer or drift instead?

05-22-2011, 10:55 PM
I think you should go in business,Randall

05-22-2011, 11:21 PM
Those bolts are filed flat so they fit tight in each notch, correct?
Correct. 5/16" bolts, filed down to roughly 1/4" square.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]
And you turn the steel plank (or plate) by hand, or just tap that with a hammer or drift instead? [/QUOTE]
It's just a bar, about 18" long. Maybe 3/8" thick by 1-1/2" wide. Started life as a post for concrete forms at Home Depot (which explains the extra holes). The other end is a similar "quick and dirty" tool for unscrewing the plugs in the bottom of a J-type OD.

I used it by hand, but you could tap on it if needed, for some extra torque.

05-23-2011, 07:02 PM
I'll take mine in red Randall. Thanks for making them!