Hey all, first time poster long time browser here, I couldn't quite find the answers I'm searching for. When driving, my tach will flicker up and down and in wondering what the cause is. I think the transmission might be slipping because this does not happen when the car has been warmed up and driven for a bit. I'm planning to change the fluid out to see if it fixes the issue. Any help or guidance is greatly appreciated

1986 iroc-z
305tpi
700R4

 

Hi Calyps0, welcome to TGO

That'd have to be one hell of a transmission slip to cause the tach to "flicker", surely you'd feel that as a hesitation while driving, yes?

I think doing regular maintenance is great and if you want to change your transmission fluid have at it, but as to your tach, I think I'd hook up one of those handheld "dwell/tach" units and see if the engine's RPMs are actually flickering, or if it's just a fault in your tach itself. The factory gauges in our cars are notoriously inaccurate and prone to several types of malfunctions.....

 

A power/signal interruption to the instrument cluster can also cause that.

 

A flickering/jumpy tach is usually a fault in the secondary ignition systems. Plugs, cap, rotor coil and/or wires

RBob.