Speedometer Reads Fast

[Dakotaj]

Well I’m happy to report that lubing the cable has almost completely fixed the bouncing. It still bounces about 5 mph at highway speed, but much better than 20+ mph. It now reads consistently 8-10 mph high, which I could see just being the tires. Much easier to tell how fast I’m going now. Thanks for the help!

I would suggest changing the driven gear. Pull the speedo and see what colour you have. Then swap out for one that has more teeth to lower reading.

 

[Ricko1966]

If he wants to correct speedo error all he has to do is change the speedometer gears in the transmission. Looks like @Dakotaj types faster than me.I think it's TCI has an on line calculator for speedometer gears.

 

[Steelbuddha]

If memory serves, the speedo drive gear at the transmission is plastic of some sort (probably nylon). Thus it would be worthwhile to pull the gear and confirm that it is 1) intact and 2) spinning freely. That done, blow a bunch of Tri-Flow down the inside of the cable casing.

 

[Long Rider]

If your speedo isn't acting the same, floating, bouncing the first thing to do is lube the heck out of the cable then do it again. Make sure the cable is screwed in all the way at both ends. Then if you get it stable (mostly) you can always change out the driven gear to make the speedo match reality.

 

[YakkoWarner]

Mine reads around +5 at highway speeds (indicated 70=65 actual for example), which is about an 8-12% error rate. However, at the suggestion of folks here on this forum I checked the odometer accuracy, and it is only 2.3% off which could be easily explained by tire size. I thought perhaps the instrument itself was just miscalibrated, but the VSS reading (pulled from the ECU using an ALDL reader) matches closely with what the instrument indicates. I havn't worked out exactly what is causing the discrepancy yet, but since I amost always have a GPS running I just trust it's speed measurement to avoid citations.