Speedometer humming, needle jumping, and then died.

So I went for a ride to visit my mother the other day, an hour and a half each way. Around the last ten minutes or less of the ride there, I heard a really high pitched humming that came and went and seemed at times to be in synch with the engine and other times not. I was concerned, but figured I'd see if it did it on the way home. It did as soon as I set off and after a while I noticed that whenever it was making the noise the speedo needle would jump like crazy back and forth, sometimes jumping 20mph from where the accurate reading was when it wasn't doing it. By the last twenty minutes of my ride, the speedo didn't work at all and the noise had stopped.
I had reset the trip odometer before I left my mother's house and it had the correct mileage when I got home.

Has anyone experienced anything similar to this? Would this be an issue with the sensor down by the wheel or something to do with the actual gauge in the dash?

 

That's kind of what happens when your speedometer cable breaks. Lack of lubrication causes the cable to bind and let loose, that's why the needle jumps around. It eventually breaks.

 

I'd bet it's the gauge itself. I have 2 XJ's that have symptoms as you describe. For me, the noise appears when the temp drops below 50(F) and moving above 20mph. On my 700, it's actually quite embarrassing as it is a fairly hi pitch sound.

It's a tough fix because dissecting a speedo is quite involved with the bezels needing to be pried back, etc.

I was able to calm my 650's gauge by removing it, turning it over and squirting just a touch of WD-40 (with lithium) between the square recessed spinner (that the cable goes in) and the outer wall of the threaded shaft. Be careful though. Not too much, you don't want that stuff getting in there and fogging up your glass.

 

Nothing against WD40 products but in a light machine oil is better suited for a speedometer cable. A heavy lubricant like lithium grease will cause excessive drag on the cable . It will work but like to use 3in1 oil or sewing machine oil.

 

I have cable lube, would that be better?

 

It was very high pitched and very embarrassing. I was glad when it finally went. Sounded like one of those motion sensor ghosts decorations that make that “ooooooooooooooooh” sound.

 

I used a tiny squirt of WD for the threaded shaft on the housing (diagram), not the cable.

Yes. For the cable, use cable lube.