No speedometer
I've a truck that does this, and I just found out that the gear->cable bit broke off, so the cable isn't turning. I'll have to fix this by pulling the transfer case's tail piece off, and removing the gear, fixing whatever exactly broke.
As far as which it is, one way to tell:
1. Set trip counter to zero(push button)
2. Pull instrument cluster. This requires a torx or hex driver. I recommend using a little impact driver or close-quarters powered driver for this, as it speeds things up a lot if you have one.
3. Remove the speedo cable from the back of the instrument cluster. This will involve squeezing the correct portion of the plastic surround which holds the cable to the speedometer. Do it right, and it'll just slide out.
4. spin the little nub sticking out of the back of the speedometer with your finger, and watch your gauge. You should see the speed jump around as you move it. Also, if you spin it a few times, you should see the odometer & trip counter move a little.
If it moves, your cluster's OK, and it's at the gear end. If nothing happens as you spin it(make sure to try both ways), time to find an instrument cluster to part out. your local JY probably has one, as this part seems to be identical across all late-80s Ford trucks.
if the speedometer moves it is in the trans/t-case output shaft.
if it dont move it is in the cable/ speedo head.




