The speedometer will stay steady, lets say 55, and then shoot up 10 to 15 mph faster and bounce around alittle, it also has some bouncing at most times but not all the time. Does this sound like a cable going bad or something else? It is an 82 w/ cruise and 114k miles. I don't know if it's the original cable but I would assume it is.

 

My spped bounse dup and down befor i changed the speedo wire.

 

Disconnect the cable from the transmission and run it with a drill motor while looking at (or having a friend look at) the speedometer. If it's still jumping the cable is binding or the mechanism in the speedometer itself is snafu'd (many $$$ to fix). You may be able to free a binding cable up by spraying 'Lock-ease' or some other such graphite lubricant into the cable jacket. If it runs smoothly with a drill then you either have a worn-out driven gear or drive gear or both or a misalignment between the two. Pull the driven gear out and check the teeth for straightness, and look inside the opening in the tailshaft housing to ensure that the drive gear is sitting squarely in the center of the opening. My guess is that your driven gear is worn out- new ones are about ten bucks from a whole host of different vendors. Hope this helps.

 

Helps alot, thanks !

 

Tak82.

You can check the speedo by testing it with a drill as described above. On your car there is an upper and a lower cable. Either one could be causing the problem.

I would check the cables first.

Things that can cause speedo bounce are as follows.

1) Defective cable (s)
2) Defective transducer
3) Speedo gear failing in transmission.
4) Speedometer. (Mainly the first worm and magnet head bushing)

Greasing a cable is a big No No too! While it may stop a cable from making noise, the cable is reverse wound and will only drive the grease in to the speedo head. This will cause the head to absorb just about any dust particle it can and eat up the first worm and magnet bushing. There are plenty of graphite based lubes for the cables that you can use, or if you insist on lubing he cable, wipe off all the excess possible to avoid costly repairs down the road.

Willcox Inc.

 

BTDT... had a kink in the cable on mine

 

When mine did that, some lubrication cured it...or you can get a new cable which isn't too expensive.

 

When myine went bad it was the cable end going into the speed control.

 

Exactly the point I was trying to make. It can either be the upper or lower cable or a multitude of other things. All of which should be checked!

Lube will help a cable be quite, and even eliminate bounce. In most case’s this will cause more damage down the road. We rebuild the speedometers here and I wish I had a dollar for everyone that was jamb packed full of hard dried out lube. The reverse winding of the cable pushes the lube in the back of the unit! It will quite the cable, but over oil speedometer assembly. In older units with oil impregnated bushings, this will cause failure even faster.

Many things can cause speedo needle bounce! Even the spring on the speed cup that controls tension for the magnetic field can cause this. The 79 Late cars through 1982 used a lower speedo face than the 1978 – 1979 early cars. The internal parts were different to counter this change. The spring on the speed cup which is driven by the speedometer first worm and magnet is not as stout on the 79 late – 82 cars. Even this can cause a little bounce in the needle. (Only when you hit a hard bump though)

Just for knowledge in the future too... We get this question a thousand times.

Q) My odometer is not working but my speedo is working fine!

A) On the old “W” Series speedometer (pre 1978) If the odometer is not working on your speedometer then it is in desperate need of repair. To ignore this is to allow for more damage down the road. The most common cause of this in a “W” Series speedometer is the first worm bushing is shot. When this happens it miss aligns with the second worm gear and eats it and the second worm gear up. Replacing the second worm gear is useless! (Kind of like replacing the tach drive gear and not the main shaft on a 1962-1973 distributor) While it may allow the odometer to work for a while, the main cause is being ignored. The first worm bushing is shot and the only way to repair this is to replace the bushing, the first and the second worm gear!

There are several shops with good reputations for building Quality speedo’s and tach’s. I’d have to say that Brian at Corvette Specialties of Md., Clocks by Roger, Valley Vettes on the west coast and us are about the oldest shops that build these things. Brian has gone as far as making parts now that GM is not making and supplying them to most shops that rebuild the units. But I believe that all of us would tell you the same thing. There are a ton of issues that come in to play on speedometers and how the work and function.



Willcox Inc.

 

Drove the car alot last night and the bouncing has almost completely stopped, but the main problem is when you get around 60 and stay there, the needle will quickly jump to 70-75 SOMETIMES. Won't do it at 50-40 or any other speeds. just 60 and faster, it will jump up there, stay there and bounce around alittle and then return back to 60. Still a cable ? I know all about cable going bad, but this 60mph thing has me baffled and that's why I thought I'ld ask, but I'll be checking the cables also.