Here in Illinois it is cold right now. Well when I first take off in the pro after sitting in the cold the speedometer, once it gets to 30mph, starts to vibrate and rises to past 140mph when I am still only going 30-40mph. It has done this for a while. And today, driving back from school, the speedometer needle vibrated so hard that it snapped and broke. Now I am without a speedometer. I can drive on it right now, thanks to the tach and knowing what speeds have what rpms. I don't know why it is doing this. I will probably just have Mazda order the needle and put it on and calibrate it. Anyone have any ideas to my delema?

 

I had this exact problem with my '93 Protege, although it never
got so bad that the needle broke.

As suggested, the ratio between the tach and speedometer is
1:1 in 4th gear. Or more properly, 100:1 (4000 RPM == 40 MPH).
The ratios in other gears are also small, whole number ratios,
although I don't recall exactly what they are. It is easy enough
to determine emperically, though.

After I computed the ratios, I made a little sticker and pasted it
right under the tach for easy reference. Everybody who rode in
my car had to ask what the little sticker with the crazy numbers
was for, and I got to tell a geeky story about how I have to do
multiplication on the fly when it's cold to see how fast I'm going.

 

So why is it vibrating like that? I am going to have Mazda fix it if it is not too costly.

 

To let you all know, I have found out what was going wrong with my car. I took the instrument cluster off and found that the speedometer cable had no greese on it. So I have made some calls and got a cluster for $35 and a cable for $15. Not bad. I had to take the cluster out to get that damn BR number to order it. So I will be getting that in a few days. Talked to Mazda and they said that they will put it in for $225. So I am having the masters do it. Since it took me almost three hours just to get the cluster out, they can have it. Now time to find white face gauges for the new cluster. Keep you posted.