To start, these are the tools you'll need. (Not shown is a heat gun that you'll also be using). Note that the speedo has been disassembled down to the outer shell with no glass or interior ring. The DIY boot will be made of 3/8" shrink tubing. There are different surface finishes and colors of tubing available. I chose a flat black for this demonstration as it best resembles the original. Use whatever you want, but it must be 3/8".
Here are close-ups of three of the tools above so you'll know what to use. They are: A 3/4" step drill bit....
Elmer's (low-foaming) Glue-All Max...
and a standard Fine Point Sharpie with the cap clip broken off and ragged edge filed smooth.
To begin, cut a piece of tubing no shorter than 1 1/8".
With your step drill, enlarge the Trip Meter hole to 1/2". This is a very small increase in it's original size and won't be noticeable. It's purpose is to allow the Trip Meter knob to move more easily through the hole.
Take the 1 1/8" piece of shrink tubing you cut and slide it half-way down a pair of needle nose pliers. Pull the handles open and stretch the bottom half of the tubing to about 1/2" so it will fit the new diameter of the Trip Meter hole. If you overstretch it, give a minute, and it will contract.
Insert the tubing into the hole until the 'short side' of the end is about 3/16" past the inner edge. The 'long side' doesn't matter. Insert the tapered end of the Sharpie (did you remember to shave off the clip?) into the tubing. As it moves in, it will stretch the tubing out to fit the hole. This next part is important: As you see in the photo, make sure that your alignment is 90 degrees with the top notch. In the following photo, note that the tubing is also at 90 degrees with the body. If you don't get this right, your results will be less than satisfactory. At this point, make sure that your Sharpie top is FIRMLY in place. Any gaps between the tubing and the metal wall will allow the glue you'll be using in the next step to seep out.
Before you perform this next step, as stated above, ensure that your tubing is at 90 degrees and the cap is FIRMLY in place. Next, turn the body up so the tubing is vertical and apply a small bead of glue around the point where the tubing contacts the gauge body. This glue foams a bit and will rise onto the side of the tubing to help hold it in place. Now, with the body still in a vertical position, clamp it lightly in a vise to dry overnight. You want the glue to stay put, so make sure the body is not tilted.
After it dries, the results should look something like this. Trim off any excess tubing that extends past the edge of the glue.
Now, clean the interior of the gauge's glass lens, drop it in and follow that with the inner ring.
With a Q-Tip, apply some ArmorAll (or it's slippery equivalent) to the inside of the tubing and on the exterior of the Trip Meter knob. Take your lower housing and place it into the upper housing while sliding the Trip Meter knob into the tubing. Line up the edges of the housings and their notches.
With the knob inside the tubing, note that the knob's bottom edge shows through. Measure 1/8" out from that point and make a mark. Next, carefully remove the lower housing while sliding the knob smoothly out of the tubing. Now, cut the tubing squarely on your mark.
Re-insert the lower housing and Trip Meter knob and the results should look like this.
Now, tilt the lower housing up and push the knob out the end of the tubing as far as it will go.
Using a heat gun held approximately 8" from the tip of the tubing, apply heat while constantly rotating the tip of the gun around the end of the tubing. Use a back-and-forth waving motion so as not to allow too much heat to be focused on the tubing. Doing so allows the end of the tubing to shrink more uniformly. As soon as you see the tip begin to contract, stop and check for fit. If you shrink the end of the tubing onto the shaft, you've gone too far. Take your time. The results should look about like this.
Now, place the top and bottom halves together and check for uniformity and fit. If the tubing bottoms-out into the interior of the knob and buckles, trim off a very small amount of the tubing and re-fit. At this point you are ready to attach your faceplate. With the new boot in place, you can no longer separate the upper and lower halves, but that's okay. You can easily maneuver the upper body out of the way to allow yourself enough room to place the faceplate and insert the screws. Good luck!
