Jefftopgun

What would cause this? It runs very smooth, just backwards, its cool to say I shift my stock c3 at (whats the last number?? 7?) like 7K, more if I feel like it, but its weird at the same time...

Any fixes, or just replace?

VetteLS6

This cant be a mechanical Tach OH god if it is you have the wrong rotation on the distributor......wow.....does 1st gear go reverse??????? OMG

redcar1979

Check the Flux Capacitor....

mdj21

what year is your vette?

you did not fill out your profile......

Fstdraw

Maybe it's not a Vette. Could be a FIAT X19. Ahhh, mid-engine, light weight and free reving. One million miles per gallon. Good days.

c3dreamer

Your thread is funny but if it really happens to you, check if you have inverse wires installation (+ wire connected where should be a - wire connected and viceversa).

For an igniition system with breaker points check the following:

1. The - wire of the ignition coil must run to the distributor points.
2. The + wire of the ignition coil must be installed to one connection of the ignition switch.
3. The other connection of the ignition switch should run to the solenoid connection that also have connected a black wire that run to the + terminal of the battery.
4. The coil wire run (center wire from distributor cap) should run from distributor to center connection of the coil.
5. A second wire, also a + wire of the ignition coil should run to the oppose connection of solenoid described in item 3.
6. Check starter and battery grounds.

Jefftopgun

Sorry, its a 75 l48 4spd.... All stock, including, until yesterday, the stock plug wires i think loool

HDFLH67

I have a '75 that does the same thing. No one here has been able to come up with a serious suggestion yet, and I have been asking for ages. If you get it fixed, I'd love to know what you found!!!

Bob Onit

you dont by chance have one of those 90 degree adapters on the Distributor for the tach cable?
Thats about the only thing I can think of
This is a very strange problem and the first Ive ever heard of

Sky65

Never heard of that one before. Is the tach electronic or mechanical, stock or aftermarket, did it ever work correctly? Where does the needle sit with the engine off, zero or maxed out?

Glass Act

Hmm... not sure what your issue is, not to make fun, but mine only goes backward after the motor quit's running.

Bob Onit

Damn Sky
Thats a beautiful 65

Sky65

Thanks. The pictures make it look better than it is. It's a 10 footer but for a driver that is ok.

ACECO

I recently have been working w/a couple forum members repairing broken electronic tachs for them. If it's an issue due to the electronic circuit board, (sounds like it) I may be able to help you out. Let me know.

Good Luck!

Bob Onit

I dont recall if the 75' was a mech or electronic tach
Can someone fill me in please?

CheezMoe

Per the Corvette black book, 1975 was the first year for HEI and electronic tac. My guess is that the TAC signal and ground wires are inverted.

LYLE

75 is electronic

ACECO

It doesn't work that way. The analog tach movement is driven by an electronic board that converts the ignition pulses into a variable signal that moves the needle. If the pulse input from the distributor and ground were reversed, nothing would happen. In other words the tach wouldn't move at all.

If the tach is moving backwards then either the circuit board or the tach movement has an issue. The movement itself is capable is turning nearly 360 degrees, but normally the signal driving it wouldn't do so. The fact that it is points toward an issue with the board itself.

You can get a replacement board for $60-75, but often these don't work as well as they could. Another option is to have the original board repaired. That can usually be accomplished for about half this cost.

Hope this helps. Good Luck!

HDFLH67

Thanks for a serious and knowledgeable reply!

1Z87L8

George definitely knows what he is doing.