The Stovebolt Site Forums The Shop Area General Truck Talk Which Grommet? How to Get Them Into The Holes?

The project I am working on is a 1940 1/2 ton...but I bet the answers are the same (or very similar) for most of the rest of the 1940's trucks.

I have attached a photo of the grommets that came with the kit from Classic Parts of America. (The oblong one for the center of the firewall is not in the photo, but I got that one figured out!)

I am starting to put a few things back together and when I went to install the speedometer cable, I looked at the hole and then looked at the grommet, and figured that I had better ask some questions!

(INCORRECT!) I assume that the grommet in the lower right of the attached photo is the correct one for the speedometer cable to go through the firewall with.

Is the grommet on the lower left the one for the main wiring harness?

What is the grommet in the middle of the photo for? (Speedometer cable!)

I figure that if I know the answers to the questions above, I will be able to figure out what the last two grommets are for.

I assume that a cut from the center to the outer edge of the grommet must be made as the fittings on the ends of the cable housing would never be able to fit through the hole in the center of the grommet. And I assume that a similar cut must be made in the main wiring harness grommet as well.

Next, how does one convince these things to go into the holes? Dish soap and water? Any advice would be very welcome!

On any vehicle that I've installed firewall or trunk grommets like those, including the AD Truck, they go right in. They aren't hard to install. No wax or soap required. Test fit them if you're worried.

Are your cables already installed? If so, you'll have to put a slit in the grommets or disconnect your cables and wires. Good luck getting the end of the speedo cable through the hole, though.

Once you slice the grommet and pass the wires thru, you can glue them back together using crazy glue(CA).

Nick, Here are a couple photos of my '46. Hope this helps? I like Phil's idea to Super Glue the seams on the grommets I ended up cutting.

Thanks for the input folks! Because of your feedback I was stopped from heading off in the wrong direction!

The grommet in the center of the photo was the correct one for the speedometer cable.

I tried wrestling the threaded part of the cable housing through the grommet in response to Otto's challenge...but I lost, and went ahead and cut a slice in the grommet.

The assistance is appreciated.

Nick

I just wanted to expand a bit on the super glue tip. For the best results, be sure to clean both sides of the split grommet with alcohol and glue it before you insert it into the firewall. Gluing it beforehand allows you to get both sides together tightly.

Allow sufficient time for the glue to set up (the longer, the better), before inserting the grommet into the firewall. If you try to glue them while they are already inserted, the rubber is under too much stress, which makes it very difficult to get a clean, secure adhesion.

I didn't have any issues with grommets for my AD, and didn't use any glue. I did slit the one for the speedo cable. When I added wires (I think it was 4) for turn signals to the main harness, I needed to ream the original grommet out to account for the larger diameter of the harness. Using a screwdriver to push the grommet in place helps if they're tight around the outside.

Be careful with super glue that you don't stick yourself to the grommet. LOL!