View Full Version : How to fix cable driven speedometer?

Night Wolf
03-27-06, 04:35 PM
The car is my mothers '89 Brougham, and it does some weird stuff....

ok, first up, it used to work, then slowly stopped working. It got to a point, right after the tranny was rebuilt, that the speedo would read exactly 12mph under the actual speed. So we brought it back to the tranny shop, they said they never touch the speedo gear, but took the car for a drive anyway, and he noted it was in fact, 12mph under the speed.

So the guy replaced the speedo gear with a different size, and at the time, it read the correct speed.

Well, as time went on (not that much time) the speedo would go lower and lower, until it would barely move. As it is right now, it stays at 0, except if you do 65mph+ on the highway, it'll go up to ~15mph or so.

Well, one time I was driving the Brougham, just for the hell of it, I put it in Neutral while coasting. Much to my amazement a few seconds after it was in neutral, the speedo registered a speed... not just any speedo, but exactly 12mph faster then what the car was doing (because of the change in the speedo gear) The speedo was quite noisy, you hear alot of sound from the cable or something, and it would move back and fourth, but it was working.

So, I have a few questions. First, why would the speedo work when the shifter is put in neutral, but as soon as it is put into drive, would it stop again? Is there something kinking a cable or something?

Also, because the speedo gear was changed to read 12mph above, I need to change that back. Finding a Brougham at a junkyard is easy enough, but how hard is it to get at the speedo gear and do the actual swap?

Another thing, the cable, I want to replace the cable with a brand new one, can they be had at Advance Auto? or is it no longer made? How would I go about replacing the cable? is it a pretty painless task?

And finally, is there a chance the actual speedo cluster is bad, causing the speedo to work when in neutral but not in drive? like, is there a chance I'll also have to buy an instrument cluster from a junkyard too?

Thanks in advance :).

Night Wolf
03-27-06, 11:36 PM
I just read that there is a vehicle speed sensor on the back of the speedo that tells the computer when the car is over 40mph to lock up the torque convertor...

with the speedo on the Brougham not working, the speed sensor never gets the message, which means the torque convertor never gets locked up on the highway....


03-28-06, 01:16 PM
I'm having a similar problem on my '89. It works, but it makes a LOTTA noise at high speeds. I plan to replace it but I have no clue how to do that as of now. I got to study my manual for a minute. But they do sell it at the Auto Parts store. I do most of my shopping at Advance Auto Parts, and they have it for $13.97.

03-29-06, 06:07 AM
You can check/replace the cable itself fairly easily by disconnecting it from the tranny and sliding the cable out of the housing. If the actual speedometer unit in the dash is bad you can replace it or have it rebuilt. I had mine rebuilt when I got my old 78 Fleetwood, it was like $80 IIRC. I couldn't find a junkyard one.

Night Wolf
03-29-06, 10:50 AM
If the cluster itself is bad, there are plenty at the junkyard (in NY, where I'll be fixing it)

I know for a fact the cable is bad, it isn't steady.

But why would the speedo barely work when in drive, then when in neutral, and cosating, would it read accurately? abit alot of noise....

03-29-06, 11:07 AM
Maybe it's just luck because there isn't any part of the speedometer that would care what gear you're in or anything like that.

03-29-06, 09:28 PM
Perhaps the torque applied to the transmission case in a gear makes it move that 1/16th inch so it doesn't connect anymore.

Night Wolf
03-29-06, 11:03 PM
never thought about that..... but thae little bit of torque shift would do it?

\I mean, even when coasting in drive, it wont register... but put it in neutral....

Thats why I was thinking its a cluster/steering column thing... I know nothing directly effects it, but what else would be causing it?