Weird speedometer problem

[schwinger]

Didn't know where to put this thread so I figure hear would be a good place. I've got a weird problem with my speedometer. Had to replace the original one because the odometer stopped working but the speedometer still worked, we'll bounced around a lot tho but it was working properly agile back. So I replaced it with one from a duster from the junk yard that appeared to be good. Installed. It and the speedo bounced again so I researched a similar problem and took out the speedo cable and lubed the core and checked for any kinks, reinstalled it and now it's smoother but way the hell off. At 60 or 70mph from what it seems, the speedo reads 30 mph and any faster it starts climbing. Is this speedometer shot or is there a way I can fix this?

 

[Prine]

Weird....I agree. The speedometer system on these cars are not too complicated...and your on the right track to your solution....but you need to consider the variables for your symptom.

The Speedocable is driven off the output shaft of the transmission, with a speedometer output gear that is Plastic....and the variable here is the WEAR, unless its brand new..

The Cable is then inserted in the end, and is driven through the Speedo Cable Housing till the Square End plugs into the actual Speedometer.

If the cable spins freely by your fingers inserted in 90% of the cable housing.....not all the way up to the cluster all the way.....you can assume your housing is ok.....

I think your output gear is worn.....or not properly engaged/clocked on the output shaft.

Best way to grease the Speedo Cable Housing is with a Grease gun....

My speedo squeeks when its below 40* outside.....otherwise its pretty steady and does not bounce alot...(not to say it doesnt bounce a little)

With more information......we can deduce your concern....No Problem.

 

[adriver]

I'm thinking it's not your cable.
Never seems to be the problem.
See how the clearance between the little ears on the back of your speedo spinning thing and round thing they surround is tight.
It's a magnetic coupling.
That space gets either dirt in the space or less likely it worn and letting the ears grab the round thing every once in a while.
Clean it and lube the shaft with LPS 1. (greaseless lube.)
then take a short piece of speedo cable scrap and run the thing in an electric drill to functional test it before putting it back in the car.
I've done lots of them like that.

I'm talking about the later square speedos.
If yours is an earlier one, they may be made different and you can't see the back of them.
I don't know.

 

[Prine]

The Cable Housing Connector that plugs into the back of the cluster (its white)....has a little Lock Tang, that is broken on some of these 35+ year old cars too.......and never fully seats the cable into the cluster causing poor performance.

 

[71DodgeDemon340]

Who needs a speedo? Lol just a good excuse to get out of a ticket.
Officer: sir is there any reason why your speeding.
Sir: my spedo just broke yesterday and i dont know how fast im going.
Officer: well make sure you get it fixed, by the way nice a body
:cheers:

 

[Rocky_JS]

Nothing has changed from the transmission if the gear was wrong it could show this type is disparity of speed from actual. This wasn't an issue before so what changed - the speedo. I'd say bad speedo head calibration. It is probably not worth sending out to be calibrated when they aren't hard to find. It is possible the cable isnt in all the way and it is skirting the outside making the speedo move.

 

[schwinger]

The cable connector is somewhat broken where it sleeves onto the hose but I have a hose clamp holding that part on so it might not be sitting in properly. The locking tab ain't broken tho. I'll fiddle around with that and see if it makes any difference And I did remove the speed gear on the tail shaft to clean and lube the cable coming up to the engine bay and the gear was not worn out. I just checked the position of the gear w/the markings and it's right where it's suppose to be with the speed gear I'm running.

 

[sireland67]

The NAPA in my local town had a cable in stock for a A body duster.
$20
Replace it.

 

[schwinger]

Ok I did a few more runs installing the speedo cable behind the speedometer a few times and still does the same thing so I disconnected it and yanked the core out of the hose and tested my original speedo with the core and drill and ran it full speed and stays a steady 70 mph. Now I did the same thing to one that's already in there and...only goes to 20 mph so I'm just gona yank that one out and install the original one back in even tho the odometer doesn't work.

Who needs a speedo? Lol just a good excuse to get out of a ticket.
Officer: sir is there any reason why your speeding.
Sir: my spedo just broke yesterday and i dont know how fast im going.
Officer: well make sure you get it fixed, by the way nice a body
:cheers:

Lol I wish it was like that! actually I got pulled over in one of my other classic cars not to long ago that I found out it was reading 10 above actual mph and I was going 80 instead of 70 and I explained to the officer I was going by what the speedo said and he gave me a freaken fix it ticket!!

 

[schwinger]

And I'll check my napa store too. I Might as we'll replace it since it is the original "aged to perfection"one lol

 

[dodge freak]

Who needs a speedo? Lol just a good excuse to get out of a ticket.
Officer: sir is there any reason why your speeding.
Sir: my spedo just broke yesterday and i dont know how fast im going.
Officer: well make sure you get it fixed, by the way nice a body
:cheers:

Yeah but what if they wanna drive it to make sure its not working :sign12:

 

[dodge freak]

i find it best to have your speedo read just a tad too high. Mine reads 2--3 mph too fast...so when I slipped up the other day and was going mid 70's in a 70 zone, the cop drove off as i went by but then turned around at the first turn around.

U remember it for a while but then as month-years ago by, you forget about it. Why I did not see the semi marked car sitting on the shoulder, I don't know, my brain is slowing down too much....

 

[schwinger]

Just got done installing the original speedo back and took it for a test drive! Working frkn great, besides the OD and no bouncing but i think the mph is 10 or 15 off since I took it on the highway going 70 and a couple of truckers were barely passing me up so I gotta figure that out and I always liked that idea dodgefreak of having it read at least 5 mph over. Ran my 69 mustang that I use to have like that and rarely got any tickets.