Speedometer Drive Gears
 

To start with, I had my speedometer checked and re calibrated, but still N.G.

Checking the turning of my cable on the dash, it turns backing up, but it does not turn going forward - at times it will click-in and turn a couple of times. Apparently this is what is making the mph numbers jump from 0 to ?? and the back to 0.

I checked the cable, it is OK - fits (locks) into the gear drive and the speedometer. I took the gear drive off of the drive shaft and it looks OK to me ( not sure what I'm looking at though) . The gear on the drive shaft slides back and forth about 38" - 1/4" .

I don't know what to do......maybe order a new secondary take off gear unit? Does anyone have any suggestions ?
Dave

Re: Speedometer Drive Gears
 

When I start on a problem like yours I would take a pocket screwdriver and put it in the drive hole while the wheels are turning (jacked up or on lift), this way I can feel if the drive gears can turn the cable
then I inspect the end of the cable for wear, most cables the inner core can be removed, then that end can be fitted into the gear shaft and checked for wear that can cause it to slip --moving it in or out to see if there is a worn spot that it slips
Also when the inner cable is out roll it on a table to look for bends and kinks that cause speedo needle wavering

sometimes the outer cable has been stretched making the inner cable too short and the square doesn't go far enough into the drive or speedo ---one repair in place of a new cable is a cut to length inner cable repair kit made longer then the "original'

Re: Speedometer Drive Gears
 

Make sure that the cable end is crimped on tight and not slipping.

Re: Speedometer Drive Gears
 

Thanks guys and 1930 Coupe for the ford barn back thread, a lot of good info. My 19 tooth gear is really warren in the center of the gear. I ordered a new gear and gasket from Mac's. I'll give it a try. I'm hoping that the drive shaft gear is OK. Looks a little warren on the front end - looks pretty good on the rear side. I can slide it back and forth about 3/8" or so, up to the clip and back. I hope that it is supposed to do that. I checked the cable turning - backing up it turns, going forward it may jump or basically not turn at all.