Source for Dowty Washer LD200 side plug ?

[BeerBudgetRacing]

Anyone know the correct size?

https://www.mcmaster.com/dowty-washers/

It looks to be 5/8 ish but I have constant leakage. Looks like someone buggered the threads at some point and clean out the treads and semi-countersunk and removed about 1/4" of the threads.

I think that is why I have a constant leak.

Any alternative ways of sealing it?

[ejsprint30]

I bought mine from Scotty Young

[Lotus7]

If I picture your issue correctly, it’s doubtful any size Dowty washer will seal a countersunk hole.
perhaps try a correctly-sized o-ring trapped in the countersink. You may have to increase the size of the countersink to make this idea work.

[EYERACE]

A ton of leaks here from the bottom of the casing going on for a year and a half
I recently.........don't ask why........had to rebuild my diff (ring/pinion) in my LD200..........and thanks to scott young at sy-gearboxes.com and Alan Oppel...everything went well.
The lower plug had a nasty leak among other problems......so I think I've got another dowty laying around if scott can't come up with one fast enough for you. I'm here to help
Using first a steel plug I got from the Taylor end of the racing world..... the bottom hole was extremely slowly tapped with heat and then the real plug supplied by scott was slowly screwed up into the casing after that....using the new dowty of course.
Thanks again Scott and Alan

[BeerBudgetRacing]

I think I've got it covered with an o ring captured by the dowty.

What surprises me is how often people cross thread and otherwise screw up these boxes.
Obviously over torque as well. Geez, take a beat and make sure you aren't cross threading.