Speedometer lag possible cause

[Steve G.]

Re: Speedometer lag possible cause

Steve-

I'm about an hour south of Ottawa. We agree on the bouncing needle cause- but that's not what the OP has.

If the cable was binding and causing under-indication- why would it been seen only under acceleration and resolve itself once the vehicle is at a constant speed?

An hour south of Ottawa? We'd go there in Jan to get a break from winter .

I don't believe his cable is binding. I was just clarifying that cables can bind and cause issues without turning in the ends in case someone reads this at a future time and assumes from what's posted that a bouncing needle must be head and can't be cable.

I agree. This is not his problem. Post #14 outlines my best thoughts for the moment on this.

[Domenic T.]

Re: Speedometer lag possible cause

Just a thought,
But the cable can be put thru the housing with the stop at the wrong end. That would cause the stop to rub.

Steve,
I've also seen my share of cold as I lived in Illinois and I also saw the problems you described. Many cables unraveled and broke in the housing.

Mike,
As far as the cable being like a rod, they really have a lot of twist in them. With one end clamped the other will twist a few turns. And I did see some start working better as the car warmed up thinning the lube. Back then in the 50's & 60's the used graphite in the locks and speedo cables.
I moved to CA and repeated the mistakes myself. Speedo worked great all the way up to Mamouth ski resort, next morning went to drive to breakfast and the cable wound up and released bouncing the needle against stop till it came off the pin. I payed on the snow and reached under my pick up and disconnected the cable. When back in the warm lands I put the needle back on and connected the cable and all worked fine again. I don't remember if I washed the wrong lube out then or later!
Al,
Hope you get this one figured out and let us know.

Dom

[Michael W.]

Re: Speedometer lag possible cause

Speedo worked great all the way up to Mamouth ski resort, next morning went to drive to breakfast and the cable wound up and released bouncing the needle against stop till it came off the pin.

That's the cable binding momentarily then releasing.

As already discussed, not similar to the OP's problem of speedo lag.

[Al R.]

Re: Speedometer lag possible cause

Just crawled out from under the car. Hooked up a drill in reversed with the wife watching the speedometer. I tried from 0 and ran the drill to max, she said needle would go to 90 and then drop back to 60-63, with the drill still held wide open. Repeated from starting speeds of 20,30,40 and ran up at variable speeds and at a sudden max speed. Always went up to 90 and then fell back to 60-63, this while still holding the drill wide open. Tried starting at different speeds and running up to higher speeds quickly without any lagging of the needle. I pulled the plastic gear out again and cannot see any damage to the teeth. Is it possible the gear is not engaging into the metal gear enough or is somehow slipping over/under the metal gear enough to allow slippage. If so, wouldn't the plastic gear show signs of damage on the teeth. I do have a slight amount of play in the drive line--ever so slight. I checked for this with a large screwdriver stuck in the trans yoke wriggling it back and forth. I thought about placing a flat washer between the plastic gear and the metal bullet to possibly extend the gear deeper into the trans. , but it prevents the gear stem from sealing at the outlet of the bullet. Would this be an option to try? I'm out of ideas.

[Michael W.]

Re: Speedometer lag possible cause

If the max speed on your drill is 1000 RPM, your speedo is pretty much spot on for accuracy.

Your first post talked about speedo lag, now it seems you're mentioning overshoot. If the drill speed was increased at a rate similar to the car accelerating, say zero to max in 5 seconds, does the needle still overshoot?

[Bob R.]

Re: Speedometer lag possible cause

My tach needle bounced around just before it broke. I think the inner cable is frayed causing the bounce.

[Al R.]

Re: Speedometer lag possible cause

Bob, it's not a bounce, the needle just lags behind on rapid acceleration or above normal acceleration and then ketches up when the speed levels off..

[Al R.]

Re: Speedometer lag possible cause

Michael, not sure. I tried another cable(repo) on another cluster speedo head and it does the same thing with the overshoot. I just assumed the rapid drill increase might be simulating wheel spin.

[Dale O.]

Re: Speedometer lag possible cause

Al,

I have the same problem you are experiencing with my 65 speedo and tach. The speedo was rebuilt and the tach was not. I talked with the speedo rebuilder and he suggested that I loosen the cable to speedo connect slightly. His thought was the cable nut may be reducing the required play in the speedo shaft. I have not had a chance to try this yet. Just my 2 cents.

Dale

[Dan H.]

Re: Speedometer lag possible cause

Al, I had problems with binding tach. I checked the length of the sqare end that goes into the tach, it was too long, causing a bind at times. Measure the depth of the sqare recepticle in speedo/tach and make sure cable end is not too long.
Dan

[Al R.]

Re: Speedometer lag possible cause

Hey Dan, not sure how to get a measurement on the speedometer fitting with it in the dash, but I'll try to take a stab at it. Dale, my rebuilder had me check that also. Mine was a little snug at both ends, loosened them a little, but still have the same results.

[Al R.]

Re: Speedometer lag possible cause

Is it possible that the output shaft could be moving in or out in relation to the driveshaft upon acceleration or kicking into passing gear? If so, this would move the steel gear also, which could possibly cause the plastic gear to ride on the outer edge of the steel gear and possibly cause the 2 not to mesh properly. But upon re-engagement or alignment of the 2 gears, would damage occur to the plastic gear teeth? Does this sound plausible to anyone? Again, searching for possibilities and cures. Al

[Steve G.]

Re: Speedometer lag possible cause

Is it possible that the output shaft could be moving in or out in relation to the driveshaft upon acceleration or kicking into passing gear? If so, this would move the steel gear also, which could possibly cause the plastic gear to ride on the outer edge of the steel gear and possibly cause the 2 not to mesh properly. But upon re-engagement or alignment of the 2 gears, would damage occur to the plastic gear teeth? Does this sound plausible to anyone? Again, searching for possibilities and cures. Al

If the output shaft were moving that much the speedo would be the least of the symptoms you'd be experiencing. If you're seeing the gear pretty much centred as you look in the hole in the extension housing it's pretty safe bet it can't walk out of contact.

[Al R.]

Re: Speedometer lag possible cause

Thanks Steve, just trying to figure out a cure. Al

[Thomas S.]

Re: Speedometer lag possible cause

New to the forum. I have a 63 that I just purchased and the speedometer is behaving exactly like what has been described in this thread. It does not move during acceleration but eventually catches up once the speed levels off. Assuming there isn't any slippage between the cable ends and gears I don't understand why a cable lubrication issue would cause this problem. I'm just trying to understand this before attempting to dismantle the entire package end to end. If the cable is correctly matted to the gears it should either turn or break. Agree that lucubration is essential, but only to prevent the cable from failing and prolonging its life.

Some feedback please from anyone that might have something to add.

Tom