Weird Tachometer Function

[jrusso07]

Hello all,

I have been living with this for a few years and haven't really thought about it until I drove the car this week. Here's the issue. When car is in neutral, the tachometer shows the correct engine revolutions (as compared to an external digital tach). It is fairly accurate throughout the rpm range. Now, put the car in gear and drive, accurate at idle, but fails to show revolutions above about 2000 rpm. Even when running it out toward "red line" by engine sound only) in low gears. Your thoughts on what might be wrong?

My WAGs... I assumed cable slippage but why not at idle? Is it In the gauge or in the drive to the gauge...could the drive gear be worn out and shows itself under load...?

[nismou20]

Could the square ended cable be so worn that at low rpm it still spins tach but as rpms increase the cable slips and out spins the tach? Square end maybe rounding in wear? Theory?
Joe, Maybe you can chuck the distributor end of cable in power drill and spin it up to see if tach works.

[Nissanman]

I would suggest either a well worn or even broken inner cable.
The frayed ends might cope with the low revs only.
Fairly simple job to check as above and replace if required.

[jrusso07]

Will pull the cable at the distributor and see what's up/drive with a power drill