Speedometer Bouncing/Odometer stopped

[JimsHot66]

At the 39,000 mile mark on my odometer the speedometer needle bounced in a 10 mph increment until I got to 39,001, then things settled down and speedometer and odometer worked normally. This morning, I crossed the 40,000 mile barrier and the same thing happened with the speedometer needle clicking and bouncing as the odometer went from 39,999 to 40,000. Unfortunately, the odometer stuck at 40,000 and the speedometer needle continues to click and bounce.

Before I contort myself digging into this, I thought I’d ask here for suggestions/experience. I’m suspecting the speedometer/odometer mechanism is locked up, but could it be the cable? If the speedometer mechanism, are these repairable or should I just hunt for a new one?

Thanks,
Jim

[poboyjo65]

Quite often the cable doesn't get pushed into the speedo good enough or far enough or,or ,or, not correctly enough. sorry for the stutter but I always check that first, pull it out ,fiddle with it & put it back in all the way. possible the square core doesn't get lined up correctly keeping it from correct entry.

[Jims65cyclone]

What John said, but it also sounds like it could be in the head, to me, since both times it happened when the 1,000 mile drum needed to rotate up a digit. Theory: the seldom used 1,000 mile drum was binding, causing the cable to twist in the sheath and either disengage the square end from the square socket in the head, damage the gear on the tranny end, or break. If both ends of the cable look good, it turns free and is fully seated, like John said, then it almost has to be in the head. Its a PITA, but I'd pull the head and try twirling the drive end by hand using a square drive bit that fits the socket. When I bought my 65, the speedometer worked, but the odometer didn't. The fact the speedo worked, and accurately, lead me to suspect the head and not the cable was the problem. I pulled the head and found some chewed up plastic gears that turned the number drums. Since neither function works on yours, I'd suspect a damaged cable, but caused by a locked up head. And that opinion, my friend, is worth every cent you paid for it.

Jim

[Caveman49]

great analogy Jim To me it sounds like the drum on the thousand mile number wheel, but like John mentioned, I’d try the cable first, it’s the easiest first step. The last time I messed with an odometer was probably back in the 60s, a lot more agile then. If I remember correctly, they had like plastic keepers holding the number wheels, and they could break easily if you weren’t careful with them.
Good luck with it, and keep us posted.

[JimsHot66]

Yep, Jim (Jims65cyclone...too many Jim's around here ) nailed it.
Pulled the cable, it looks good, and reseated it. Still bouncing, stuck at 40,000. Pulled cable again and put a small screw driver into back of speedometer to see if it was jammed (in hindsight this really doesn't tell me anything). Returned cable, still bouncing. Removed cable.

Now I'm looking at two options:
1. Replace the speedometer only. I see an NOS one on ebay for $100...should I jump on this and get it?
2. Redo my gauges and replace/return all the gauges to the gauge cluster. Right now the temp, volts and oil pressure are on a separate cluster. I've wanted to have all the gauges up in the gauge cluster, but don't want to go digital. This might be a good time to do this. This could also morph into getting rid of the woodgrain finish on the interior, which to me, seems out of place in this car.

I haven't done any research other than the quick search which located the NOS speedometer. Any good sources for gauges/speedometers?
Anyone change the woodgrain around the gauges, heater controls and radio? I'm thinking it would look better in black. I doubt it, but, are there adhesive vinyl kits for this?

Thanks,
Jim

[Joe Travers]

If it were me, I'd pick up the NOS speedo while it's available, but that's just me.
I like stock stuff. As a Comet owner, get it while you can.

Joe

[JimsHot66]

If it were me, I'd pick up the NOS speedo while it's available, but that's just me.
I like stock stuff. As a Comet owner, get it while you can.

Joe

Yep. Thanks Joe, this confirms my initial gut reaction to just order it. For $100 it's pretty low risk. It should be at my house by April 12th.

Jim

[poboyjo65]

I'm a tightwad,,,,,I'd have to take a peek at the driven gear on the cable at the trans before I spent a hundred bucks on a new speedo. I've had them do some bouncy things with a warn out gear. had one that bounced & ran a little slow,the highest point of the bounce was 10-20 mph slow at hwy speeds,then when I let off the throttle it would read right & not bounce until I got back on the throttle,then it would go back 10-20 mph slower & bouncing again.

But I'm also lazy so I'd try my spare speedo before I crawled under the car to check the gear

[Jims65cyclone]

I agree with Joe. Comet stuff doesn't fall from trees, so you should probably grab it while you can. If you decide to go a different route with new instruments, I doubt you would have any trouble turning that speedo around on ebay again, maybe even for a tiny profit. I'm planning to do a revamp of the instruments on mine eventually, taking some inspiration from what Tom (tomb22) did to his. Might be some food for thought.
viewtopic.php?f=9&t=13294&start=105 starting about half way down the page.

Jim

[JimsHot66]

I'm a tightwad,,,,,I'd have to take a peek at the driven gear on the cable at the trans before I spent a hundred bucks on a new speedo. I've had them do some bouncy things with a warn out gear. had one that bounced & ran a little slow,the highest point of the bounce was 10-20 mph slow at hwy speeds,then when I let off the throttle it would read right & not bounce until I got back on the throttle,then it would go back 10-20 mph slower & bouncing again.

But I'm also lazy so I'd try my spare speedo before I crawled under the car to check the gear

I'm cheap and lazy too... I'm 99% certain it's going to be the speedometer since the odometer locking at 40,000 seems to have caused the problem. Also, the drive gear in the trans is only about 1,500 miles old and the cable seems fairly new. I feel that getting this NOS speedometer for $100 is a win as it, or the broken one, will add to my paltry collection of Comet parts.
Jim

[Joe Travers]

Comet stuff doesn't fall from trees, so you should probably grab it while you can.

Why Comet owners are born hunters!
Seriously, I get a huge kick out of finding a good part once in a blue moon. It's the little things that make it worth while to me.
Like the two 80 year old guys that followed me home couple days ago just to look at the car and hear it idle

Joe

[JimsHot66]

The NOS speedometer should be here tomorrow (Monday). Should I lube this anywhere (odometer gears?), or just install it? If lube, what type?

Thanks,
Jim

[Joe Travers]

Shop manual calls for a small amount of graphite lube on end of cable.
Insert cable into speedo housing and give it a slight twist to make sure it is seated.

Joe

[poboyjo65]

I don't think liquid lube would be good, would attract dirt and dust and would hold it and gum up.the graphite is what I would use if anything in the Speedo.

[JimsHot66]

The NOS speedometer had clear grease in the opening for the cable. I cleared some of the lube to check the opening and installed as is. Works great! Car now has 00002.8 miles on it.
Jim