RPM Flux
 

I was driving this weekend an noticed that my RPM needle on the gauge jumps around a little. Typically, when I hit a bump or other sudden movement of the car (not acceleration or deceleration). Is this typical of the older (1976) gauges? I have not noticed it in any other car but then again I am much more mindful of this cars every movement.

Mine has had this problem for two years. ASG has not found the source which is likely a short somewhere. The tach has been sent out for refurb and still it does it. Only when hitting bumps. Hit another bump and it operates normally. Some rainy day I could trace the wiring I suppose.

Can't say I've ever paid that much attention to mine, but it's a mechanical gauge, so I wouldn't be at all surprised if it bounces when you hit a bump.

I had this issue. Turned out to be a loose connection from the big cable coming out of the starter. Connection looked fine, but cable pulled right out of connector when Vicegrib gave it a slight tug.

x2 on a loose connector... check grounds.. etc.