1972 Standard dash E body.

As far as I know it has the speedo cable that came with the car. It is well lubricated with the graphite speedo lube that comes in a tube.

It's been to Instrument Specialties 2 times and the speedometer checks out as good.

I've had this problem with an AUTO trans and now with the MANUAL trans. I've also had 2 DIFFERENT speedo gears in there when I changed the rear end gears.

Tom at Instrument Specialties suggested that I trim 1/16" off of the end that goes into the speedo. I have 2 spare speedo cables that I will probably experiment with instead of grinding on the one from the car.

Have you guys had to trim the speedo cable and what was the result?

Thanks

Some replacement cables are made extra long and you trim to fit.
If the cable is slightly too long and bottoms out in the speedo It could cause the cable to bind and whip around inside the housing.
Also take a look at the entire cable housing. If it is melted or bent too sharp It can/will bounce.
Try rerouting the cable to make the bends as gradual as possible (especially at the speedo end)
while keeping as far from exhaust pipes as possible underneath.

Thanks,

This seems to be an on going problem with these cars. I do have a spot on the outside of the cable that is showing the metal cords, but does not seem to have been burned. I cleaned the inside well, blew it out and then coated everything with PB graphite spray. I trimmed a little off of each end and put a dab of grease under the ferule that is on the speedometer end.

We'll see.

Thanks

Let us know, I just put a new cable and speedometer in my 51 and it's doing the same thing.

Since it's such a PITA to change the cable, I ordered a $38 one shipped from Ehrenberg. I did that 2 hours ago and when I just checked it showed that it was shipped. I've bought a few things from him and have never been disappointed. His stuff isn't any more special than the same thing somewhere else, but he's a Mopar guy and I figured what the heck.

I'll check this cable vs. mine and trim it to match if it's long and then probably use it.

Just to add...

Make sure your block to firewall ground strap is real good. If not the speedo sheath becomes a ground and that is NOT a good thing.

I did have a too long center that I made and it bounced the speedo too. Cut it down and that fixed it.

So the mechanical speedometer in our old cars is pretty simple.
In the transmission is the pinion. If it is worm because it was not adjusted to fit in the teeth will cause a bouncing speedometer.
The cable inside its cover needs to be lubed with graphite. Grease and or oil is affected by temperature. This could cause a bouncing needle.
The head of the speedometer has a cup and clock spring. There is a bushing in there that get worn and allows things to wobble causing needle bonce.
Also the magnets over time loose their magnetism and then the speed shown on the needle is lower.
O yeah
1000 RPM = 60MPH
If the needle sweeps to the right then the cable rotated clock wise.


So having the gauge rebuilt is expensive but unless you want to take the chance of ruining it its best to let some one with the proper tools do it.

I'm confused. Aren't the cables usually pre-lubed with a special grease, and not a dry lube like graphite. Aftermarket ones I've bought were. I seem to remember pulling the cable from housing on OEM ones and they were greased. I recently bought a NOS one for my Power Wagon. I don't really need it right now, but it was priced right. I'm going to pull the cable and see if there's grease on it. Even after all these years there would still be some.

There are some greases that aren't too effected by temps. I've found "Fifth Wheel Grease" to be very good for applications like this. I use it in my power window gears and tracks on my Diplomat. Very silky regardless of temperatures.

If the speedo has been tested good and the gizmo at the trans is good, then it can only be the cable.

#1 Make sure there are no hard bends or kinks along the length of the cable. Any bends should be smooth and wide.
#2 Any damage to the cable sheathing should be inspected. If it's broken internally and binding against the cable, there's yer problem.
#3 I'm not a fan of the dry lubrication. If you live in a moist climate, it has a tendency to get clumpy and not be much of a lubricant. I'd suggest if neither #1 or #2 are your problem, then remove the cable, clean it as best as possible and use an actual lubricant like a light motor oil, Fluid Film, heck, I've even heard of people using cooking oil because it's so light.

Even if you do use a heavier grease for the cable (I have actually used wheel bearing grease, personally) the speedo may be sluggish at lower speeds, but it certainly will not bounce anymore. Chances are you won't be using the vehicle in the winter anyway, so you'll probably never see any ill effects.

Every cable I remember working on was greased, and the 3 or 4 new ones I bought were also. Sometimes they come with a grease packet.

As stated earlier, sharp bends are the enemy. The hardest is usually under the dash, right behind the speedo....you want as straight as possible there.

The new cable I bought for my 51 was not lubes, or if it was I couldn't tell. I lubed t during install. Might have to pull it out and do it again.