Technical Articles

Installing a 100 MPH Speedometer for next to nothing.

by Paul Eschenbach -- 8/28/00

Alright, before anyone gets upset, I'm not condoning speeding or defiling speed limit signs. What I am saying is that the stock 85 MPH speedometers that came in the 78 & 79 Broncos may be a little "inadequate" for those of us with modified Broncos and a little bit of a lead foot. Anyone who has ever driven on an Interstate in a large city such as Atlanta, GA or Houston, TX knows that if you're only doing 85, then chances are even little old ladies are flying by you like you're standing still.


So, you need a better speedometer to measure your speed? Well, you're in luck. The 100 MPH speedometers installed in 1973 to 1977 Ford F-Series tucks is a direct bolt-in replacement for the "slower" Bronco units. All you have to do is remove the instrument cluster from one of these trucks and replace your speedometer with the older Pickup Truck unit. There are a couple of thing to keep in mind, however, when replacing your speedometer with one of these older units. 


First, The location of the high-beam indicator light on some of the older model trucks have a smaller hole or no hole at all for the little blue high-beam indicator light. With one of these older units, you will have to drill or enlarge the existing hole directly over the "50" so that your light will be visible. I believe that some of the later models (maybe the 76 & 77 models) have the same high-beam indicator light as the Bronco. In this case, no modifications will be necessary. 


Second, you will need to set the mileage of the new speedometer to match the mileage on your old one. If you need to turn it back, I can not tell you how to do that because I would be breaking law if I did. I can tell you that the same method that will turn the speedometer back will also move it forward. However, if all you need to do is move it forward, you can stick a reversible power drill with a tapered drill bit in the back of the speedometer until the mileage matches your old one. The revisable drill method will not turn the speedometer back, incase you were wondering.


So how much will it cost? I bought mine for $25.00 in a local salvage yard. g



Future Project -- Some time in the next 12 months I'm going to try to find a more modern instrument cluster that will fit in a 78-79 Bronco. I may even try to retrofit a digital instrument cluster!