For unknown reasons, the previous owner drilled a hole straight through the back of the cab. It's towards the passenger side, right through the back interior panel and out the sheet metal. It's about 3/8" in size. I can't fit my hand between the bed and cab to get to it from the outside, so I'm going to have to get at it from the inside. To plug it, I was thinking of a solid rubber grommet, but I can't seem to find a solid one. I thought maybe fill it with permatex gasket maker, but I don't know how well that will hold.

Does anyone have a good way to plug this hole so it's watertight? Thanks for any help.

 

If you can get in there, if its only 3/8", try a small shot of silicone....

 

What if you get some JB Weld / Cold Weld and seal it that way?

 

Here's a plug from McMaster-Carr.

3/8" 0.38" 0.42" (steel) P/N 2598K21 $4.41 (s/steel) P/N 9191T31 $7.98