Are tach cables directional?

[dennis1200]

This may be a total beginner question, but I searched the forums and didn't find anything specific (most people posting still using gennys, getting advice to put in an alternator instead but nothing mentioning anything different about the tach). I'm looking to get a tach cable for my 1972 Ford 4000 with a 3-cyl gas engine. I recently replaced the instrument cluster since the old one was mangled, but got one with a counter-clockwise tach since the electrical system has an alternator now instead of the original generator. Are tach cables direction-independent or should I get a different one? The instrument cluster I got is E5NN10849BA and all the gauges are working great, but rpms would be nice to see too. Does the cable just hook right into the alternator?

 

[Sean in PA]

If you got an alternator with the tach drive (quite a bit more expensive than a plain alternator by the way) then you should use the original instrument cluster and cable since the tach drive on the alternator should spin the same way as the tach drive on the generator did.

If you got an alternator without the tach drive then there is nowhere to attach the tach cable once you replaced the generator with the alternator. The 1975+ 2600/3600/4600 series tractors that used an alternator and a ccw rotating tach used a tach drive that was driven off of the oil pump and had a fitting on the side of the engine block near the oil filter to connect the tach cable to. The earliest of the 3 cylinder thousand series did not have a block that the oil pump driven tach drive could be added, but the later ones did, so your 1972 engine probably has a plug that you could remove to install the tach drive. If you are lucky then the oil pump drive gear already has the square recess to drive the tach cable and all you need is the external part of the tach drive, but if the pump drive gear doesn't have that recess you will need to pull the oil pump and replace the drive gear.

The part number for the tach drive assembly is 84405438. Messicks has one in stock for $170.00

The part number for the proper oil pump drive gear, if you need one, is 87800008. Partspring has a number of them in stock for $73.00 a piece.

 

[Sean in PA]

To answer you original question, I am not sure if the tach cables are directional, but if you do get the oil pump driven tach drive for your new ccw instrument cluster, you will want the tach cable from the x600 series as well, as it needs to be shorter than the one that goes all the way up to the generator.

 

[RodinNS]

Yes, tach cables are directional.... they are a wound cable so if you apply torque in the other direction it will unravel and break.

So, you have the new style cluster with the counterclockwise tach..... I HOPE you have the newer style engine block with the native spin on
oil filter and the welch plug below the filter. If you have the old block it will have a threaded plug with an internal hex. That won't suit
what you're trying to do. But if it's got the original 72 engine it should be the 'new' block. So what you have to do is remove that welch
plug and extract the oil pump drive shaft. Then you replace with an oil pump drive shaft for a 4600 or so and ADD an engine tach (angle)
drive. Get a new tach cable for a 4600 and hook it all up. You should be good to go.
What you can't do is drive this cluster off the alternator even if the alternator has a drive.

Rod

 

[RickB]

That tach drive assembly is available in the aftermarket for about 1/3 of the NH price. IIRC, Atlantic offers it.

 

[dennis1200]

I thought I had a native spin-on filter (it is a spin-on in any case), but it looks like a hex plug beneath it unfortunately. So if that's a no-go, I just won't have a tach, not the most important thing in the world.

 

[RodinNS]

Interesting. I haven't seen that setup before where the old block had the spin on filter... and it does not appear to be an adapter. Sadly
though, you do have the hex plug... so no tach drive in that hole.

Rod