gday,
When driving at a constant speed my speedo twitches both ways like its having a fit. It used to do this when I had a bad ignition module. Now its doing it again. Could it be another bad module? Or is there other things that can cause this?
cheers,
heb.

 

Not sure why ignition would be related to the speedo.

How much does it wiggle around?

Check your speedo cable.

 

The speedometer is cable driven from a connection to the driver's side of the transmission gear housing. If your speedo is spinning and/or 'surging', then replacement of the cable will likely fix your problem.

The tachometer is electrical and driven off of the trailing ignition coil, so you may be thinking of the other.

Sometimes speedo cables can get crimped during clutch replacement or other tranny work and cause this problem. Could also be that the connection has simply come loose where it screws into the tranny - get under there and have a look. The dash connection to the instrument panel is a PITA to get the little clip free from the speedo back, however. Take your time on the replacement cable installation,

 

I have put a little STP oil treatment down the speedometer cable to clear the problem up. A local mechanic does a car care clinic on the radio. He uses STP for lubricating speedometer cables, not as an oil additive.

Another time the speedometer itself was screaming loudly as the needle swung. I figured it was shot, so I pulled it out, blew the dust off, and put some 3 in 1 oil on all the moving parts. It's been working fine for a few years now. I'm at 195K miles.