Packard Forum Index » V-8 (1955-56)

Parking brake was fixed today, just a couple new cotter pins. The next item on my to do list is to fix the speedometer. It’s working “somewhat” but has a mind of its own. Sometimes it’ll bounce around 40-50mph but lately it’s been pegged at 100mph. It also sounds like a seal getting electrocuted and gets louder or softer depending on throttle position. Am I looking at stripped gears, or can we get a replacement cable?

Could be cable but also there is a somewhat hidden oil hole for lubricating the bushing holding the part the cable end spins when inserted in the speedometer. After all these years the bushing probably needs a few drops of light oil. In the 55-6 units the hole is in the square part of the casting on top and visible but somewhat blocked by a screw. The speedo does not need to be removed to add oil and a needle type applicator should be able to reach the hole. The oil hole has a felt wick to hold and distribute the oil but in some speedos there may be a dirt cover over the felt. Suspect a cover if after a drop or two the oil does not seem to want to be absorbed. If the bushing is totally dry it may also help to use the needle applicator to get a drop or two directly at the spinning piece at the end of the casting where it rotates in the bushing.

There is also a worm gear and train inside the speedo to work the odometer section and its grease could have dried up. A symptom if that has happened is the odometer wheels may jump or if the gear train is totally frozen and a gear has possibly been damaged, the wheels do not work at all. In either case to clean or repair the gear train the speedo will need to come out.

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H

Isn't there magnets that work the needle

There is a spinning magnet on the end of the piece the cable turns in the bushing. It does not touch but rather spins around on the inside or outside of a spring loaded aluminum cup which is attached via a shaft to the needle. The spinning magnet sets up an eddy current around the cup which will try to drag the cup along with the magnet thus moving the needle. As long as the magnet spins consistently and smoothly the calibrated but light spring loaded cup and needle responds appropriately -- faster the rotation, stronger the eddy current force so higher the needle will move against the spring. If the magnet spin is erratic because of a dry bushing or a problem with the cable and magnet stops and then suddenly jerks with a quick and fast motion as something breaks free the cup reacts violently. That action can slam the needle into a stop and because the cup is a relatively heavy mass and the point where needle is pressed onto the shaft is very small the joining point on the shaft can break as the needle suddenly stops and often will twist off.

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