El Camino Central Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
131 Posts
Discussion Starter #1
Hello everyone. I've been pulled over three times in the past few months, thankfully I have not had any points against my record, but every time I get pulled over the officer tells me that I am going ten miles an hour faster than my speedometer tells me that I'm going. now here's the question could a old speedo cable be streched to where it is ten miles an hour slow?:dontknow: I need A quick reply because I want to get the new cable today before I get pulled over again.
 

·
Registered
Joined
·
190 Posts
Possibly but unlikely. The actual speedo sounds like the culprit. Check to see if your speedo resets back to 0 with the key out of the ignition, and that it doesn't go too far or far enough. My speedo is fast by 5 miles per hour, and I can see the needle on 5 mph when the key is out of the vehicle, so check the needle with the power off, and the engine on and in drive the second time, if you dont notice anything weird get the cable.
 

·
Registered
Joined
·
5,048 Posts
The cable has nothing to due with this, your speedo is mechanically driven, 86-87 Elkys are electrically driven. Changing tires from the OEM size (larger or smaller diameter) can cause the speedo to read off...also if the trans has been changed and the speedo gears are not correct, this could be the cause, also changing rear end gears to a different ratio. Look at it this way, a driveshaft turns at the same rpm at one end as it does the other, the transmission is what determines the rpm of the driveshaft. The speedo cable works on the same principle as a driveshaft. If the speedo needle is showing 10mph when not moving, than yes, it can be reading 10mph off through the entire range. If you go to www.maliburacing.com and click on the tech page and then click on speedometer gear selection you may be able to figure out how to correct your problem...but on the other hand you might want to see if a reputable trans shop can calibrate it for you...one speeding ticket would probably cost you more depending on where you live.

__________________
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
 

·
Premium Member
Joined
·
457 Posts
I did a tranny swap on my 81 and the speedo was way off. The needle would peg out at 85 on the on ramp to the highway. What I did was compare the odometer to the mile markers on the interstate. On a good long run I kept a log of the odometer reading at the mile markers, plotted them and got a consistent 15% difference regardless of speed. I confirmed this with the radar traffic signs for the lower speeds. Yes my needle resets to 0 when not moving. Mechanical speedo and odometer.

You can get a gizmo to correct the cable RPM coming out of the trans. Somebody posted a link on here a while back. I do not worry about it since I do very little highway driving.

Found one of the links http://www.speedometershop.com/ratio.html
 

·
Registered
Joined
·
2,938 Posts
Pull your speedo housing out of the trans. (easy to do), count the teeth on the driven gear that comes out with the housing. Go to any GM parts department and ask for a gear with more teeth. My guess is you need two more teeth but you will need to try it and see. The gears are also color coded but it is sometimes hard to tell the color. Counting the teeth is a slam dunk. Hope that helps.
 
1 - 5 of 5 Posts
Top