What would make my tach bounce.....it starts when I get to aroudn 45 MPH (usually), doesn't matter what gear, but my tach will go crazy.....

 

Could it be a bad battery ground possibly? maybe not grounding enough when I get more voltage going?

 

You would see other problems also if it was a bad battery ground such as lights not working correctly. I'm no expert, but I guess I'd check for loose connections/bare wires.

Mark

 

OverClock, I have the exact same problem after that guy messed up on my cam. I'll floor it and as soon as it shifts out of 1st at about 45 it goes wild. I think it maybe because of the loud knocking from the rockers on my engine. The timing is all screwed up, so I figure the knock sensor and the computer go nuts. When I get my cam fixed this summer hopefully it will go away.

 

I would start by checking the connections. You may have a loose signal wre too...

 

WEll guys, here's the odd thing. The fan motor went out on it, and I replaced it...no more jumping tach