Speedo question

[JIm Duda]

When I purchased my 86 GN it was already cloned as a GNX. The company I bought it from had put in a GNX dash but not all the gauges worked. The speedo was always reading 15-25 mph more than I was actually doing. The needle was bouncing and only accelerated when over 20 mph. I am having the oil pressure gauge changed and had the boost gauge fixed. The temperature gauge shows hot then goes back to normal when I tap the gauge. As for the speedo, could it be the cable or something else? Any ideas?

 

[novaderrik]

a bouncy needle on a mechanical speedo gauge is usually a speedo cable problem.. does the odometer read correct against mile markers on the highway?
if so, then the cable is working right and the drive and driven gears in the trans are right for your gears and tires and there is an issue with the needle in the speedo.

 

[dennisL]

What brand of gauges are in the cluster (VDO, Stewart Warner, other)? I ask because I have a GNX style cluster with VDO gauges and might be able to help.

 

[JIm Duda]

VDO gauge. As for the mileage part, it appears to be accurate. I was thinking that since the engine has been rebuilt 3 times since I owned it and other modifications that were made then it might be a gearing issue.