Speedometer accuracy varies with temperature

[Stocker]

Since I got my '85 back on the road, I've noticed strange behavior from the speedometer. In colder temperatures, the speedometer reads about 5 MPH fast, but when warm (~65°F or higher) it'll be generally accurate. The past two days, it'd be off on my way to work and back to normal on my way home.

Is this potentially a simple lubrication issue? I have to pull the cluster anyway since a light bulb burned out in it.

I had to remove the speedometer when I replaced the heater core a couple years ago, but I didn't notice any issues for the couple months it still ran after that, so I'm thinking it's from having sat for two years. It has occasionally had the issue where the needle will shoot up to the high end at very low speed, but it's only done that once since I started driving the car every day again - in the past it was just on the first couple drives after being stored for the winter.

[friskyfrankie]

Since I got my '85 back on the road, I've noticed strange behavior from the speedometer. In colder temperatures, the speedometer reads about 5 MPH fast, but when warm (~65°F or higher) it'll be generally accurate. The past two days, it'd be off on my way to work and back to normal on my way home.

Is this potentially a simple lubrication issue? I have to pull the cluster anyway since a light bulb burned out in it.

I had to remove the speedometer when I replaced the heater core a couple years ago, but I didn't notice any issues for the couple months it still ran after that, so I'm thinking it's from having sat for two years. It has occasionally had the issue where the needle will shoot up to the high end at very low speed, but it's only done that once since I started driving the car every day again - in the past it was just on the first couple drives after being stored for the winter.

Yeah a through lube and replacement couldn't hurt! See where you are at then.

[gadget73]

The one in the Towncar gets really bouncy and goofy when its cold. Not sure if that one is just cable lube or inside the speedo lube but either way my problem and yours are likely both that the oil is now closer to adhesive than lubricant.

[friskyfrankie]

I've heard some good things about LIQUID BEARINGS (which I believe is a fully synthetic oil) that should not gum up or turn solid in cold temps. Hopefully, someone here can tell us if this is accurate.

[sly]

I used red and tacky axle grease thinned (cleaned) with WD40 to lube the speedo head in the 88 MGM I had. Never had an issue after that. I've read that clock oil (for pendulum clocks) works well since it tends to stay in place even though it's thin. I would also suspect that home HVAC fan motor bushing oil would work great as well.

[Stocker]

Thanks - clock oil sounds like a logical choice for a speedometer.

Where would the oil need to be applied (and perhaps as importantly, are there places to make sure oil doesn't get on)?

[sly]

Just the cylinder that the cable goes into. You'll need to get it between the outer (static) and inner (spinning) shell of said cylinder. Don't get it on the plastic gears. I don't think it would damage the plastic gears, but they don't need it.