No plug in transmission opening, is one needed?

[TinMan Trvlr]

I enclose a photo of an open threaded hole in the red adaptor between the Allison 3000 transmission and the ISL-9 engine. Should there be a cap or plug threaded into this hole to prevent dirt from entering the drive train?

[Mr_D]

Not supposed to be one in the hole. I've had three MH's with Allisons, 2-3000's and now a 4000, none have had plugs in the hole.

[Gary RVRoamer]

No photo that I can see, but don't worry. If no fluid comes out, the hole is fine as is.

[YC1]

Very common panic feature installed to scare us. This comes up several times a year. You are fine.

[RKins]

Yup, I asked the same question - no plug needed.

[Skip426]

The hole is threaded to allow the installation of a plug IF ! ( and only if ), the engine is installed in equipment that may get into water deep enough to cause issues or if the engine trans have a wet clutch .