Sluggy/sticky speedometer

[cewyattjr]

So I recently worked on my W123/300d trip odometer which was slipping. I pulled the cluster and replaced the reset lever, springs. Also (horrors?) sprayed WD-40 on those gears. I tightened a slotted brass screw just on the side of the trip odometer assembly.

Trip odometer working great now. Calibrates fine with mile markers on the road.

However, having replaced the cluster, the Speedo is behaving in a most funky way.

I'll get up to highway speed and the needle will tend to "stick" at some value (say 55 Mph) and hang up there for a while before coming down. Like I'll be at 10 Mph before the needle "decides" to come down. Or it might stick at 30 for a while.... you get the idea. There is full clearance between the needle and the speedo face.

Any ideas? Maybe I did some WD40 damage? Is there something I can adjust with this instrument I may have abused?

Thanks,

Chuck

[Biodiesel300TD]

Maybe try lubing the speedo cable. Remove it from the transmission and the back of the speedo, and spray your favorite lube in the speedo end and turn the cable inside the sheath, adding a little at a time untill you get stuff comming out the other end. Then keep turning it untill the trans end quits dripping.

[cewyattjr]

Well... here's the curious thing to me. If it were the speedo cable wouldn't it affect the odometer performance as well, or not? I'm thinking it has something to do with the speedometer mechanism itself?

[Mustang_man298]

Originally Posted by cewyattjr

Well... here's the curious thing to me. If it were the speedo cable wouldn't it affect the odometer performance as well, or not? I'm thinking it has something to do with the speedometer mechanism itself?

I think your cable is fine, if it was sticking the speedo needle would be all kinds of jumpy, and if it didnt work nothing else would.
You mention you sprayed it with WD40, so I think you have 2 possibilities right now.
1. There is excess oil that has gotten or never been wiped out of the area where the magnetic coupling is, causing a fluid drag against the rotating half from liquid between the halves (this happened once on a car I had).
2. The WD40 is a thin solvent like oil that may have washed out the lubrication in the speedo needle bearing, causing it to drag against the rotating half of the coupling (it doesn't take much at all for this to happen). It would need just a very little bit of lube, a very small droplet of light machine oil or aviation instrument oil on the tip of a sewing needle would be plenty.

[cewyattjr]

Hey thanks, Chris. I will definitely look into that. I bet yer right!

I've found it really difficult to loosen the little screw that holds the coupling housing on the back. They managed to put a small phillips head on a screw that seems really torqued tight! I assume I'd need to get into that in order to do the little lube-job.

Anyway, the other thing is that this behavior developed over a period of a day or two after I performed the odometer service. So it wasn't immediate, it kind of gradually got more sticky.

thanks!

Chuck