for some unknown reason my tach cable broke again on my 74 and about time i do this myself instead of paying the shop $150 for the labor. Is thieir a down and dirt quick way or do i need to drop steering column and everything just to get to this thing?

 

remove driver seat from '74 C3 cabin.

smaller hands-fingers may fit up behind tach to pry retainer away & cable out of tach. If not, drop column a bit & move instrument cluster forward a bit.

vert has additional under-dash bracing; makes job tougher.

 

Hi,
It's a good idea to see what the 'clip' at the tach is like so you know what to do with your fingers once you get them in the right place.
Regards,
Alan

 

I have a tool I made to remove the cable.
Without a tool the best way I can think of is to remove the cable end from the dist and have a helper hold that end and be ready to pull when you release the tach end of the cable.
Disconnect your battery,lay on the floor looking up and with a long screwdriver depress the clip holding the cable,tell your helper to pull.
I think I have a pic of the clip , I'll see if I can find it and post it.

edit-the clip is on the bottom side of the cable,just push it towards the tach housing

 

terl30,

My instrument panel is out, so I took some pictures to show you the clip that holds the cable to the tach. Picture 1 shows the clip in the locked position. Picture 2 shows the clip being held down to unlock the cable. Picture 3 shows the cable unlocked and free to be removed.

Ron

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Hi Ron,
I think this is the second time today I've said... Nice Pictures!
Regards,
Alan

 

Hi Sarge,
Looking at the distributor end of the cable...which direction does the shaft turn?
Regards,
Alan

 

If you don't have a buddy handy, just unscrew the tach line from the distributor and tape some fish tape to the end of it. Now run that over your windshield and down into the cockpit. With one hand, push on the release at the back of the tach and with the other hand, give the fish tape a very gentle tug. It'll pop right off. If you're worried about angle, run the fish tape around the water neck over the thermostat to give you more of a straight line angle when tugging. The modern fish tape is very smooth and will not mar or scratch anything. String will also work. It doesn't take a lot of force to separate the tach cable from the back of the tach. Then pull it through the firewall leaving the fish tape in the firewall and tape the end of the new cable to the fish tape and pull it back out of the firewall and screw it to your distributor. 15 min. Done.

 

OMG guys awesome thank you so much i got her changed in less than 20minutes so much easier when i knew what i was looking for!! Beautiful pics RON thanks for your time also!

 

counter-clockwise
in other words ... if you wanted to test cable & tach head ... pull cable out of distributor ... lightly chuck core into reversible drill motor ... operate drill in REVERSE. A drill spinning about 600rpm will display about 1200 at tach. If you poke a matchstick into dist's tach drive (cable removed) ... the matchstick will rotate Clockwise when as motor turns over

Note camshaft spins at half engine rpm ... cam & dist drive gears are 1:1 ... dist shaft also spins at half of engine rpm ... dist tach drive gears also 1:1 ... so tach cable (core) also spins at half engine rpm ... tach head is designed to display 2X core rpm. So when you're cruising at 2500 engine rpm ... camshaft, dist shaft & tach core are each spinning about 1250 rpm ... tach displays about 2500.

and yes, those are dandy pics Ron!

 

Where do you guys get your Tach Cables at? I have done a quick search and haven't located them yet. Are they all the same length?

TIA Jon

 

i thought that after unscrewing the cable from the tach, the drive cable could be slipped out of the sheath just by pulling it.

 

Yeah, that may be true. But if the cable is broken within the sheath, you would still need to disconnect the other end of the sheath to retrieve the other part of the cable.

 

Have you found out why you have had to have it replaced so many times?

 

I would do a search for the Lars paper on Corvette Distributer installation, it may not be oriented properly and may have too much of a bend on the tach cable.

 

Agreed.

 

Not necessarily.
Most correct cables have a small ferrule crimped onto gage-end of core; prevents pulling core out from dist-end.

 

I just wanted to update this thread with my own experiences hoping to help someone out by making a difficult job easier. First off i followed the directions above, remove the seat, dropped the stearing column, removed the screws from the drivers side dash so it might give you a little room from behind. Now i'm not a big guy so i was able to wedge myself on the floor looking up and with one arm attempting to get to the cable and the other pushing the dash forward to hopefully buy myself a little room for my hand to get to the cable. Unfortunatly for this excersize my car is a convertible and i see the brace mentioned a little further up in this thread. There is also a big bundle of wires that is right in the way that didn't want to move much. After several attempts there was no way i was able to get my hand up to the clip to remove the cable never mind putting the cable back on. So I decided to try to attack this thing from another angle. What i did was ball up two rags and placed one between the upper dash pad and the dash around the middle and the other between the dash and the gage bezel again around the middle. This was enough to pull the upper right conner out a couple of inches. Next I removed the wiper switch and bezel. Then I reached in through the opennig where the bezel was and the cable was right there! I was able to push the clip and remove the cable with one hand. Removed the other end of the cable and pulled it through the hole in the fire wall. I took the new cable and threaded it through the hole about six to eight inches. Went back inside the car reached in through the wiper bezel hole found the cable and slid it on. The whole procedure of replacing the cable portion of the repair took less than two minutes. I was even able to place the bulb and socket back in the hole for the emergency brake and replace a light socket that would not stay in it's hole. I hope this helps someone with a job that is a real pita. Oh one other thing after i put everything back togeather i noticed my emergency bkake light is always on. Traced it back to the distribution switch block. One step forward another step back.

 

Thank you very much for the post. I have a 69 roadster and ran into the exact issues you mentioned. The brace and the wire cluster blocking access from below.
I ended up pulling the center bezel, dropping steering column and loosing the tach/speedo dash cluster to get access to the tach table.

Was a quick swap once I got access. Thank you again!