How To: Ford CMP "Blitz" miscellany

[Jacques Reed]

Good Day,

Just finished shortening the speedometer cable for my F-15A.
I am reasonably happy with the results and learnt a lot along the way.

Things to consider if you get one made up:

What type of tang tip is used at the transfer case end? With or without a shoulder?
Without a shoulder the tip goes 8 mm further into the driven gear and, if not allowed for, will result in 8 mm less engagement at the speedometer end. As I used a tip without a shoulder, the ferrule to tip distance was 24mm, but if I had used a shouldered tip the distance would have been 16 mm.
I did, however, allow 2 mm end clearance on the shaft at the speedometer drive to prevent the shaft end pressing on it and causing drag.

I found out that on the small transfer case ferrule on a 0.25" casing the shouldered tip could rub at the top of the ferrule so I am guessing the shouldered type was used on the larger 0.45" casing with the larger ferrule.

Note: Since posting this, I noticed the tip was contacting the casing- and not the ferrule, so on that basis after I removed the broken casing it looks OK to use a tip with a shoulder on the small transfer case ferrules as long as the casing is not inserted all the way into it. About where I put the mark would still allow for clearance and adequate grip on the casing.

Besides the speedometer end nuts being different between a Ford Commercial and a round Military Style speedometer, the ferrules are also different.
A Ford has a thinner flange, about 0.5mm, whereas a round gauge has a thicker one, 2 mm. This was apparent when I screwed the nut all the way home on the Ford ferrule that I used and it was still loose on the gauge. I cut off the flange from the round gauge ferrule, as I could not remove it anyway, and used it as a spacer.

The distance the shaft extends past the ferrule at the speedometer is also different. 15 mm for a round gauge and 8 mm for a Ford.

I used JB Weld to attach the tang tip. I didn't want to try to re-stake it and possibly have it way off centre or split the tip. Will see how it works out. I set it up in Vee blocks to keep it concentric with the shaft while the epoxy set. It seems a strong bond but I don't want to over stress it testing it. If it doesn't work out at least I have enough good info to get one made up.

Hope this is of some interest.