My tach suspiciously started working about a week ago and last night when I was just warming up the vette it quit again. I put a drill motor on the cable and it shows the tach working inside, so guessing the bronze cross gear(or bushing?) is bad. The question is... "Can I just unscrew that fitting out of the distributor while it is still mounted to the engine or does this mean I need to take the distirbutor out?" And if it will come out while the distributor is still on the engine is there a tool you can get to pull it out. It appears to have a large screwdriver slot of which I don't have anything the size.

Thanks for any answers.

 

from the pictures ive seen the tach gear should come out, but the gear on the dist. shaft, that will require removal of the distributor.

the tach gear looks like a speedo gear in a transmission...hope this helps, im sure someone knows more about it than i can explain

 

I would pull it out. It makes the work on the distributor much easier. If the gear is gone chances are more of the dist. needs some work. Get it out where you can easily work on it. It is no problem to remove and reinstall the dist. Just make a detailed diagram where everyrhing is pointed and reinsatll in the same way. Re time the engine when all is back together. I had to replace the dist. shaft also when replacing the gear.

 

The big bronze piece can be unscrewed with a quality made putty knife/gasket scraper, anyway that is what I have used. I have had to replace the tach drive gear and shaft in my 68 and 70. As easy as these gears are to remove, I don't know why they were excluded from the lubrication maint area of our owner/service manuals. When you remove your tach drive gear you will most likely see broken gears on this unit. The shaft is probably ruined also. You would be surprised to look in a paper copy of the Corvette parts manual for Corvettes and see all the different distributor shafts. The difference is the piece that is brazed to the top of the shaft. All the tack drive gears are the same and the shafts are the same, only the top piece is cut different for different Corvette engines. If you replace this shaft you can take yours to a shop and have your old top piece brazed on your new shaft. The replaceable shafts are for standard and high performance, but not made specific for each individual Corvette engine. You can also send your distributor to a business in Florida that specializes in doing all this for you including replacing the two bronze bushings in the distributor. If there is a broken gear you should remove the distributor for cleaning of metal pieces and to view the distributor shaft out of the distributor. The gear on the bottom of the shaft comes off after the pin is removed. Look for the dimple on mark on the gear--when you put it back on this mark must line up with the rotor. Also note which end is up on this gear when reinstalling it.

 

71-LS5, If your interested I have a restored 1111464 0C9 (correct for a 70 LS-5) and I would take yours in on trade. E_MAIL DIRECT!! if interested!!
redvetracr@msn.com

 

Looking at pictures of the tach gear I can see why the distributor shaft needs to come out and why there may bemore damage upon inspection. I appreciate the answers.

redvetracr.... I'll send you an e-mail about your distributor.

 

Just a thought - i've had 2 different car's tach's fail. In both cases, the bronze gear "rounded" out, allowing the square cable to turn. In both cases, I simply removed the cable, unscrewed the big bronze "keeper", replaced the gear and thrust washer, lubed, and reassembled.

To date, both continue to work perfectly and there was no need to remove the distributor in either case.

Just a thought ... I think GM designed the shaft to be the weak link ...