19Tyler74

Hello all,

Got the new tach cable in the mail today, hooked it up, and it's still not working.

I spun by hand the end that plugs into the distributor and it causes the tach needle to move... However when the cable is screwed onto the distributor, nothing happens on the tach.

I have disconnected it, moved it around, etc. with no results...

Could it be the distributor - or does anyone have any other advice/tips on the issue?

Thanks!

19Tyler74

I think I will have to replace the distributor tach drive coupling/gear - any advice on how to do this?
Do I need to pull the distributor to do this?

Thanks!

MelWff

Remove the coupling with the distributor on the engine, check the internal gear also, if internal gear not damaged no need to pull distributor.

19Tyler74

how do you remove it - is it just threaded? large screw driver?

C3batmobile

I'm having the same issue. Old cable was noisy, decided not to oil it because I read that that could end-up damaging the tach itself. So, I drove with the old cable disconnected at the tach for a while and ordered a new cable.

Before installing the new cable, I hooked the old cable up once, but it did not operate the tach. I finally installed the new cable recently - and it won't work either. I also disconnected & re-connected at the tach, still nothing.

I saw in another thread (http://forums.corvetteforum.com/c3-g...ach-noise.html) that maybe the ends of the aftermarket cables are possibly 0.040" too long, so I may try a adding a washer at each end next.

I'll be watching this thread for any other possible fixes - and will report back if the washers help.

19Tyler74

Please keep me posted!

I took the cable out loose and moved it in and out at different lengths and had no response on the tach... so from other sites I have read, it's most likely the coupling/gear.

There is a large slot going across the coupling, so as I mentioned above, I would think it twists out... but I'd like to know before I potentially would cause any damage by doing it wrongly...

Easy Mike

Drive cable must seat securely in the rear of the tach. If you've pulled the inner cable out, it is probably not seated in the rear of the tach any more.

Brooklinite

Yes, and yes.

The teeth on the gear are likely damaged. With a little luck the main shaft is ok, if not you'll have to pull the distributor and get a new shaft as well.

robert.sperry

This is a very common problem with the tach drive distributor design. The bearing for the cross shaft wears with time and age and eventually damage to the cross shaft teeth occurs resulting in loss of tach drive. There is a good chance that the damage to the cross shaft teeth have also damaged the mating teeth on the main shaft. If you replace the cross shaft (can be done with the distributor on the car I am told) and the main shaft teeth are damaged the repair will not last very long until the new cross shaft teeth are damaged. I would look at the big picture - how many miles on the car and has the distributor ever been disassembled, cleaned and inspected and re-lubricated? It may be better overall to pull the distributor and send it to someone who will disassemble it and inspect for main shaft gear damage as well as wear to the upper and lower main shaft bearings. I had this done to the distributor on my 74' when the tach quit working. Total repair cost for complete disassembly and repair including a new main shaft and cross shaft was about $200.00.

Paul L

Words of wisdom. Been there, done that.

redvetracr

where exactly in the exploded pic above do you see a bearing?

19Tyler74

Vette has close to 80k on it - the tach has not been functioning for years... when I inherited the vehicle and I inspected the issue, the orig. cable was intact, but the part that threads onto the distributor was broken off/missing.

As I mentioned, the cable is hooked up to the tach gauge and when spun moves the needle just fine... but when hooked into the distributor nothing happens.

I read up on it and have found as others have mentioned on this post that often the 60's-74 vettes have the issue where they tear up the gears over time.

From the above pics (thanks!) it looks as though the housing is just threaded in - so did you just use a screw driver to remove it from the distributor?

C3batmobile

My tach worked with the old cable, it was just noisy. A washer on the tach end of the cable did not help.

However, I did remove the cross shaft 'worm'? gear and it is worn around the center of the gears - I wonder if that happened, or was worsened by having disconnected the original cable to quiet the noise?

Anyway, I'll try just replacing this piece, though I realize that the gear driving this one may also be damaged - which I meant to try to look at through the hole where the worn gear was - and if it is damaged, I'll just go ahead and swap this distributor with the HEI replacement (with mech. tach drive) that I already bought from E-bay.

I know that switching to HEI is controversial on the forum - so I may learn the hard way.

I do appreciate everyone's comments and opinions - and I do enjoy working on this car - it sure is a blast to drive. Every time I return from driving her, I'm thinking the same thing - "worth every penny, even for the fuel, and worth every occasional frustration or repair".

Paul L

From the above pics (thanks!) it looks as though the housing is just threaded in - so did you just use a screw driver to remove it from the distributor?

Yes, just a large screwdriver.

C3batmobile

Well, looks like I can't just replace the gear, since I can't find them for sale - and they would likely cost as much as the HEI distributor that I bought a while back.

I suppose I will run without a tach a while longer, while I save-up for a timing light in preparation for installation of my HEI mechanical tach drive distributor.

I hope that goes well......

Paul L

I don't know how you reached that conclusion re parts.

http://willcoxcorvette.com/product_i...ducts_id=24522

C3batmobile

Thanks Paul 74 - I didn't even try the Corvette specialty shops, I just did a general search for that part for an Accel distributor of the 30100T model.

Maybe I will learn this time.

I really appreciate you taking the time to help me (& maybe others) out on this. Looks like my original? distributor might live a bit longer.

Thanks again!

wombvette

Word of warning. Dont ever just change the cross gear. You will be doing it over again, and again, and again. Do it all and do it right.

19Tyler74

Also, Ecklers.com has tons of parts - including the parts that you and I both need in regards to this issue.

C3batmobile

I was afraid of that - Thanks wombvette.

Thanks also for the parts heads-up, 19Tyler74......

The adventure continues ! Long live the Corvette adventure !