Hello! I finally got everything buttoned up on my '52 Plymouth Cranbrook a few months ago, and actually got a chance to drive it. I put over 100 trouble free miles on it, and everything was working fine until the speedometer stopped working. Here's what happened... I was driving along at highway speeds, and I noticed a faint clicking coming from the instrument cluster. Next day, the needle started to bounce around a bit, especially at slower speeds (30 or less). Then the needle started staying put until I hit 10mph or so, then it would shoot up to 60 or so and settle down at whatever speed I was driving. Finally, I came to a stop sign, and when I took off, the needle stayed where it was. I just pulled the cable. It's not broke, and it appears to be 100% intact. I ran it through the firewall and connected it to the speedometer and ran it with a drill. It worked intermittently, still bouncing around, and it seemed to get caught on something every so often. Any idea what may be the issue? I'm going to clean and lube the cable with graphite and see what happens. I had a speedometer issues with a '51 Fleetline that I no longer own that was fixed by removing and lubing the speedometer itself, which was a ROYAL pain in the ass. That speedo was hopping around and making loud howling noises. I'm hoping that I will not have to do the same with the Plymouth. Thanks... Chris A
could be the odometer is stuck, they do that...grease gets to be 60 years old, and doesn't work so good any more. I'd take it all apart, but then I'm not afraid to take stuff apart. If you aren't comfy working on things like that, you might need to send it off. but usually the odometers aren't too bad to work on, it's the speedo mechanism that can give you a lot of grief.
Thanks for the reply. Did some more digging and found an additional turd in the punchbowl...this car has a T5 swap with an S10 tail shaft, and it appears as if the speedometer jamming up may have moved the speedometer gear on the shaft in the transmission. It was clipped into place, shimmed, and epoxied, but I can now barely see it through the hole for the cable drive...it's been pushed towards the front of the transmission about an inch and half. Looks like this will turn out the be a bigger fix than anticipated...not like that EVER happens...
The problem is inside your speedometer. You must open it up to diagnose and fix it. Don’t worry; speedometers are not as complicated as you think. In fact, they are really very simple. The cable spins a steel cup. The speedometer needle is attached to a magnet inside the cup. It tries to keep up with the spinning cup but can’t because it is held back by a little spring. If the spring breaks or just comes loose, the needle will flop around a few times and then, as often as not, get stuck somewhere. I might be nothing more than that. Dirt of old grease can interfere with needle movement, too. In which case, you just clean it and put it back together. At worst, some internal piece is broken, but you can probably get one from another Mopar speedometer from the same period. It will not be hard to replace.
Jumpy speedo needle is first symptom of dry speedo cable. Try greasing the speedo cable. Detach cable from transmission, pull out inner. Wipe it off, grease with speedo cable grease. Do not grease the top 6" to 12". Put it back together, should be good for another 50 years. Speedo cable grease comes from auto parts stores, used to be $1.79 a tube (lifetime supply). If the cable is rusty, kinked, broken, you need to replace the whole thing.
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