My tach quit, on my '74 BBC.,

I pulled the cable off the distributor. The cable seems to spin freely, with minimal resistance. The question on my mind is, does the cable slide in and out of the sheathing, freely? In other words, are you supposed to be able to freely pull the inner cable out of the sheath, easily? Or is it supposed to be fastened on the other end?

 

It pulls out from the side that plugs onto the Tachometer

 

if it broke you can pull it out and see the brake, but you will need to pull the other end to get the rest of it out, unfortunately. I just replaced mine last week. If you pull your drivers seat its a lot easier to contort yourself to get under there. One member had the great idea of doing that and also laid a folding lounge chair sticking into the drivers compartment to make it easier to lay on and slide up under the dash to work on it. it saves the back for sure.

 

The tach cable is a PITA to get out of a C3 dash....especially in an A/C car!! You just need to depress the tach head retaining clip and pull the cable away from the tach head. The cable will easily remove from there.

Is there a problem with the tach/cable, or were you just doing 'due diligence' in checking it and possibly lubing it? If it was working OK, I recommend that you reconnect the cable to the distributor and leave it 'as is' until you experience a fault.

 

In this case, the inner cable pulls out, easily, from the end I disconnected from the distributor. But I didn't want to pull it too far, in case I caused further problems. I don't know if it is supposed to be fastened or clipped in at the dash end, or if it's meant to slide freely.

I took it off to check because the tach suddenly quit working. I don't know where the problem is.

Next step, I can try spinning it with a drill to see if I can get a response.

 

Your tach cable is broken inside the sheath. You will need to pull the cable from the rear of the tach housing and remove the rest of the cable from that end. The new one inserts from the dash side. You ONLY need the cable, but you may have to purchase the cable/sheath as a set. If you can get the cable separately, put the two halves of the old cable together to measure its length (end-to-end). If the new cable comes to you 'dry', lube it with DRY graphite powered lube...not oil or grease.

 

spin drill in REVERSE

 

It won't do anything with a broken cable. And if you can pull part of the cable out of the sheath from the 'tach' end, it's broken.

 

I have confirmed the cable is, indeed, broken. I didn't want to pull it out, at first, until I knew it was OK to do so, without potentially causing harm.

From the looks of it, to get the other end of the cable out, I'll have to pull the dash, to get to the back side of the tach. From what I see, there's no getting to it, especially on an A/C car, by reaching from underneath.

A question for those of you in the know - are all these cables the same length? Or do I have to measure (thus requiring disassembly) before ordering a replacement?

 

look it up for your year, my 68 had a few different lengths available..it turned out that the shortest one fit the best on my car. I dont know about a 74. You say the dash has to come off, is there ducting in the way??? mine is all right there, with the seat out I can lay on the floor and its just a minute to connect and run it out the firewall. It actually takes longer to pull the seat and the shielding than replace the cable.

 

Hopefully your cable casing is in good shape, has not been "over flexed" to accommodate a improperly installed distributor, and has dried lube that seized the cable and caused it to break. That would be your best situation as you could source a new inner cable, which you will have to cut to fit. Remove the old casing from the car and visually inspect. You may need to use solvent to get the old, dried up lube out. I use GM recommended "Lubriplate" grease on mine, which looks like a creamy white grease. Only grease (sparingly) the first half of the cable as you insert it in the housing.
If you must replace the cable, try to locate a known original 69-74 part or have one custom made. I have a known, correct replacement from about 1985 which I will get you measurements from and post tomorrow. Length and distributor placement is critical on the C3. If the distributor is out of place, you will have to bend the cable to make it fit. All the replacements available from the venders are too long. Even if you get the GM replacement for the original 6480240, you will get the upper speedo cable for 78-81(?) with cruise control, which is about 1-1 1/2 inches too long. I just went through this with a friend and we were amazed that no one (that we could find) offered the correct length cable. If someone knows of a correct replacement, I would like to know about it.

 

That scenario happened to me also. Bought a new tach cable but didn't get around to installing it for a couple of years due to Backitis, went to install it this year and it was a couple inches to long, found a corvette vendor that had an adjustable cable for around $10 and matched it up to the old cable and cut it to length and stuck it in the old housing, worked perfectly. Can't recall the vendor i bought the cable from. Paid around $22 for the long cable plus $8 shipping, WHAT A RIPOFF! And everybody sells the to long cable, WHY?
Found it, Corvette Central.
Part Number: 211001
53-82 Cable Repair Kit $10.00 $7 Shipping

 

Here are the measurements I promised. Inner cable, the one you will have to cut to length and install the tip for tach end, is 21 inches long (tip to tip). The outer housing is about 1/2 inch shorter at 20 1/2 inches. I've noticed many venders offer a 90 degree adaptor for tach drive distributors. I suppose if the distributor is installed a tooth or two off and you had the longer cable, that would help. Distributor placement is so critical that if you have the distributor drive gear is installed 180 degrees off, it will not allow timing to be properly set and tach cable to line up straight.
As for the replacement inner cable, I have heard many complain about a "cheap replacement" with the plastic tip that you have to heat up the metal cable (after cutting to length) and insert into plastic tip, melting the glue to bond. If you have a original cable, It will have a plastic tip on it and all the GM replacements were of that configuration. GM replacement inner cable was once available under PN 6477499. I imagine that number has changed many times over the years, but a cooperative GM parts man could search the history for you. Don't be surprised if it has been discontinued without supersession by now, though. I don't think GM has produced a car with a speedo cable in many years.

 

Thanks for the thoughts, guys.

I don't believe the cable is over-flexed. It seemed OK and moved easily enough. Of course, I'm not familiar with how much these can be flexed, so I can't say for sure.

Seems like it would be easier to pull the dash than the seat (partly because I don't have much room to set the seat in the garage right now). I'm also no huge fan of lying on my back under a dash any longer. When I was 20, and quite slim and pliable, I didn't mind things like that. Now - not as much.

Interesting about cables being too long. What I don't understand, though, is how to deal with it. The cable end I currently have has no attachments. It simply looks like it's been pressed into a square cross section, towards the end which goes into the distributor.

I have no idea if the tach, itself, has seized. I would need to get at the cable to see if things spin up.

Any suggestions where best to look for the part? Jegs? Summit? Ecklers?

 

Local NAPA, Advance, Auto Zone, or O'Reilys should have a listing. It will be a universal Speedo cable, probably 80 or more inches long just as GM offered back in the day. I would not suggest asking for a Tach drive cable. It will just confuse the parts guy. Corvette venders may have a listing.
What you describe is correct for the distributor end. When you remove the end at the tach, it will have either a glued on, plastic tip (original type) or a crimped on , metal tip as some replacements have. I prefer the plastic tip.

 

Call willcox, get the tach cable. Bad news is to get the dash out the steering column has to drop, and if the wheel hits the seat, then the wheel has to come off or the seat has to come out.....can you rent a kid with a good back to crawl under he dash...preferably one with a brain...when I say kid I mean anyone younger than us....IF you do pull the dash, yo may want to check or replace all the dash bulbs while its out, that way you dont have to go through this all again for just a bulb....