Possible Speedometer Problem

[minifridge1138]

Hey everyone,

Since I bought car (3 years ago) the speedometer has been kind of sporatic (bounces around +- 5 mph). The faster I drive the more it jumps.

This morning, the speedometer was dead at 0.
After a couple of miles it started to work a little.

It won't go below 30 mph. From a dead stop, the speedometer doesn't move until I get above 30, then it works normally. As I stop, the speedometer hits 30 and won't go lower.

I have a replacement cable i'm going to install tomorrow.
The cruise was gone when I got the car, so I only have a single cable going from the transmission to the back of the gauge.

2 questions:
-do you think the cable will solve my problems
-is there anything that I need to do to calibrate/reset the speedometer

Thanks in advance.

 

[J Koehler]

The new cable should solve your problem. make sure to use very light lubricant on the cable. some use graphite. There could be other problems like a worn plastic gear in the transmision. A worn plastic gear is easy to replace you just need to get the right number of teeth on the gear. To replace, remove the retaining bolt and pull it out of the transmision. Becarefull of the O ring. The unit that holds the gear can be replaced also if required. I think corvette centeral carries the gears. If the cable does not work I would pull the gear out of the trans and check the gears. If bad count the Nuber of gears and the color fo the gear it self.

Good Luck
Joe

 

[J Koehler]

No adjustment of the speedo is reqired

 

[6880 Mike]

Lube your existing cable. That might be all it needs.

 

[J Koehler]

Lube your existing cable. That might be all it needs.

I agree, but if the cable is not spinning there has to be some breakage/slipage somewhere since the system is straight mechanical.

 

[Vettehead Mikey]

As I stop, the speedometer hits 30 and won't go lower.



2 questions:
-do you think the cable will solve my problems
-is there anything that I need to do to calibrate/reset the speedometer

No.
Your speedo is farqued and needs to be removed for an overhaul.

 

[minifridge1138]

Speedometer cable is in and it works.
It is still a little jumpy, so I think i need to lubricate it some more.

The bad news, while I was under the car I found out that my master cylinder and heater core need to be replaced.

I know what i'm doing for a spring project.

Thanks for your help!!!

 

[Evolution1980]

The bad news, while I was under the car I found out that my master cylinder and heater core need to be replaced.

How did you tell the heater core was bad from under the car? Either way, that's an "Ughh" job

 

[Vettehead Mikey]

Speedometer cable is in and it works.

You said previously that the speedo still indicated 30mph even when the car was stopped. A bad cable cannot cause this.

 

[minifridge1138]

The speedometer problem was the cable. When I pulled it out the needle dropped to 0. Gauge works with the new cable.

While I was under the car I noticed coolant. I found the source of the leak: a missing plug on the bottom of the floor pan. Sure enough the passenger carpet was damp so I need a heater core.

 

[gmjunkie]

You said previously that the speedo still indicated 30mph even when the car was stopped. A bad cable cannot cause this.

Oh but it can!!Just depends whats up with the cable and if it is creating a bind at the speedometer head!!I've seen it several times,Chevy P/U's are the worst for it,but any mechanical type head will do it!!

 

[Vettehead Mikey]

Whale oil beef hooked!