FJ40 Speedometer doesn't like the Cold (1 Viewer)

[CrankySheds]

Greetngs all.

My '72 FJ40 today lost it's speedo needle. It has shown an inexplicable sensitivity to the cold lately. When the temperature outside nears 32F and I get up to close to 40mph, the cluster starts making a racket and the needle starts bouncing around. Today, when it wasn't that cold, the racket and the bouncing started sooner. I had someplace to go, so I kept on going. The racket grew worse and the bouncing violent, and - lo - the needle just fell off. The racket continued, but wasn't/isn't persistent. It seems to die out after a period of "warming up", but I can't think of a connection between engine temperature and speedo temperature.

I suspect the connection between speedo cable and cluster is the issue. The odometer is still turning over the miles. Before I remove the screws and peer behind the cluster and really screw things up, I thought I'd share what happened and see what this expert community has to offer.

This isn't something I've seen reported elsewhere, which suggests it might be a rare event. Yet, it seems so harmless as to be simple to fix and more routine than it appears.

Like I said though, I'm not presuming. I'd rather get the views of knowledgable people first.

 

[tlc762]

My guess is the original grease on the gears is dryed up like mine was and the cold temps make it worse... I started to hear a clicking sound while driving and noticed the tenths wheel was turning but wouldn't turn the mile wheel over. After a little kroil on the gears everything worked again. There are several good threads that detail the disassembly and reassembly of the speedometer and odometer on here-just search for them...
HTH,
Will

 

[CrankySheds]

Thanks for the tips and suggestions. I don't recall hearing clicks; more like a jarring whirring sound initially that sometimes goes into overdrive if I don't let off on the gas and let the speed decrease. In the past, it's always sorted itself out. Now that it not happening. It goes from first stage noise to gawd awful racket in short order.

Anyway, after doing some more research in older threads and finding loads of useful info here and there (not sure how I missed it all initially but the encouragement to find it gave me the confidence to keep looking) I detached the battery leads, removed the two screws on the cluster face plate and removed the cluster. I didn't pull it out entirely to detach the leads to the gauges; just enough to get a light shining behind the cluster so I could see what my fingers were grabbing from below. It took some practice to get my left hand under and up behind the cluster and point the light in the right spot. (I need to practice working with a light in my teeth.)

I unthreaded the speedo cable cap and removed the speedo cable. Nothing looked all that dirty or worn. There was no gunk to clean off. The tip of the speedo cable was square and shiny, suggesting to me that it was clean and/or worn at the tip. Not sure if the noise was coming from the tip of the cable not being fully seated into the back of the cluster, but that is my guess. Hence, I'm wondering if the appearance of a seemingly clean speedo cable at the end is actually what a badly worn cable looks like.

I shot some aerosol white lithium grease into the speedo cable. I did this a few times to make sure it was well-coated and replaced it into the back of the cluster. I returned everything to its place, reconnected the batter and took it gingerly for a spin.

It's not too much warmer than it was yesterday, so I didn't know if crossing my fingers would help any.So far, no noise and the odometer still turns over the miles. It looks like things work.

Unfortunately, I discovered that the speedo needle didn't fall off - it broke off as the base. ACK!!!

Anyone know where I can get a replacement speedometer needle?

Thanks again!

 

[cruiserboy14]

Did you find a fix? My speedo jumps too, before it broke, much like yours. I’ve tried multiple speedo cables.

 

[Ming89FJ62]

you most likely need to remove the cluster and the speedo then disassemble and clean the odometer then put everything back together again...use search for a step-by-step how to. won't take long it really is a job. Just remember to disconnect the battery first

 

[Marn0]

Did you find a fix? My speedo jumps too, before it broke, much like yours. I’ve tried multiple speedo cables.

Pull the dash out and remove the speedo. Apply some WD40 or similar oil liberally to help wash out the fluff ect and to lubricate the gears. Spray some down the cable itself. This should resolve the problem

 

[POPO AGIE]

Never had a problem with the speedometer in cold weather, but when it was -40 and the seat did not give I knew the starting was going to be a problem. I would get it running and have to wait before letting out the clutch because the oil in the drive train was too thick. I would put the transfer case in neutral and the transmission in gear and work the clutch and throttle to keep it from dying and once it was able to idle with thicker oil I would let it warm up.

 

[flx]

The original posting make me think it's the copper spring that is failing.

FYI the speedo (not the odometer) works with a copper spring that pulls the needle toward 0 and the needle is linked to the speedo cable with a magnetic connection. When your speedo cable rotate it pushes (through magnet) the needle toward the 100mph and you have a correct reading of speed thanks to a precise calibration of this spring.

This copper spring is very fragile, my original broke by itself after it sat for 6+ months not serving during a renovation of my 40. To keep my dash original/period correct we tried to move the mechanism with the spring from a brand new speedo to my old one... We broke the new one.
Long story short don't mess with this spring, don't touch it and if yours is broken I see no way to fix it, it's far too precise for our dirty full of grease hands.


The odometer does not depends of this spring to function so you have a way to diagnose where the issue comes from :
odometer + speedo not working = speedo cable problem
odometer working, speedo not working = copper spring mechanism not working properly
odometer not working, speedo working = odo gears used or full of dirt