It seems like my firewall has self healed the hole where the tachometer wire feeds through.
Burdar (thanks,Darren) sent me a pic of where it goes through on a Challenger but my firewall does not have a hole in the same position. And I cannot find the hole where it came from. The tach wire has been disconnected for 5 years now so my feeble memory is no help.
Thanks in advance if anyone has a picture or a description of where it goes.
Craig

Someone must know. The FSM doesn't seem to.

It feeds thru the fuse block, the lowest hole in the block, part of the wiper motor plug on 73-74s

Grey wire.

Craig, my '73 challenger (w/ '74 rallye wiring) doesn't have a special hole for the grey tach wire, it goes thru the terminal block; it's the upper left wire (next to the purple one) in the connector closest to the brake booster. I know this is chall info, but I'd swear my '74 barracuda was identical.

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Craig, my '73 challenger (w/ '74 rallye wiring) doesn't have a special hole for the grey tach wire, it goes thru the terminal block; it's the upper left wire (next to the purple one) in the connector closest to the brake booster. I know this is chall info, but I'd swear my '74 barracuda was identical.

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Here's the picture I sent to Craig. It shows where the tach wire comes through the firewall on my 73 Challenger. I think we may have discovered another difference between early 73's and later built cars. My car also doesn't have an extra ground wire off the back of the engine like the later 73's have.

I think I am going to drill a new hole where yours is and be done with it.
The tach wire on my harness has the grommet attached to the wire still so it obviously went through its own hole. I probably have something else routed in its place.
My 72 FSM shows tach wire in cavity 20 (Next to the purple wire mentioned before). My 73 FSM shows that this is the A/C clutch.
A new hole will work just fine.
Craig

I looked at my new harness as well. The gray wire right next to the purple wire goes to the oil pressure gauge.

And you would be correct, the grey wire on top IS for my oil sender. The tach wire is in the opposite (bottom) corner of the same connector. My bad, I didn't trace it out carefully enough. My '73 has a dimple where yours has a hole. But my car didn't come with a rallye dash, I added it and harness,etc, from a '74 donor. Now here's the other weird part, my 1973 wiring schematic shows the wire in the connector, but my 1974 (same year as my wiring)FSM shows the wire routed off by itself.