Speedo not working?

[Edward M.]

OK, I'm confused, which is my normal state. The speedo on the 74 454 / 4 speed car is not working, and I can't figure out why.

The cable was bad when I got the car, so I replaced it with a universal / cut to fit cable. I have driven the car with the instrument cluster out of the car and the speedo cable connected to the trans. I can see the end of the speedo cable turning at the dash.

I put the instrument cluster back in (I HATE working under the dash of these cars) and connect a drill to the end of the speedo cable at the trans. Spin the drill and the speedo moves.

I even disconnect the speedo cable at the trans, jack the rear of the car up and support the trailing arms, and get under the car with the engine running and the car in 1st gear (my wife is in the driver's seat) to insure that the speedo gear in the trans is turning. It is.

So, everything works as separate systems, but not as a complete system. What gives? What am I missing?

[Joe L.]

Re: Speedo not working?

Ed-----

Based upon exactly what you've described, the only thing that I can think of is that the speedometer DRIVEN gear has been "stripped out" where the squared end of the cable engages it. If this is the way things are, you would still see the gear turning. Also, when you hook up a drill to rotate the cable it would work fine since, in this test mode, you're not relying on the speedometer gear to turn the cable and activate the speedometer.

Sometimes, a stripped out DRIVEN gear cable end is very hard to see. I'd just replace the gear and go from there.

[Jon S.]

Re: Speedo not working?

Or maybe the cable is cut a little too short, so that it doesn't engage both ends when it is all assembled.

[Joe L.]

Addendum

By the way, I should have mentioned, just because you can see the cable turning at the dash end does not rule out the possibility that there is a "stripped out" shaft on the driven gear. Even with a stripped out shaft, unless it's REALLY stripped out (which is rare), the speeedometer cable will usually turn. It just won't turn in a manner which will effectively operate the speedometer.

[John O.]

Re: Speedo not working?

Hi Ed

You say you replaced the cable with a universal cut to fit cable? That right there sounds like it could be the problem. Like Jon said, it might be to short. I would do what Joe said. Buy a new drive gear and replace it and buy the right speedometer cable already made to length and put that in.If the cable is to short, it won't go into the drive gear enough or the speedo enough to make it work. It's worth to buy both items correct for your car.They don't cost that much.

Good luck........John

[Edward McComas]

Re: Speedo not working?

BINGO! That was it. Thanks Joe.