1971 replacing Tach gear in distributor

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Jun 22, 2013 | 07:04 PM

jbakyy

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From: Graham NC

1971 replacing Tach gear in distributor

Hello,
I just replaced the tach gear drive in 1971 and realized that the disty gear is also stripped or frayed. Can someone please help me to understand how to replace the gear in disty? Thank you

Jun 22, 2013 | 07:22 PM

TimAT

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From: Gladstone MO

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There are 2 gears in there- one comes out by removing the coupling the drive cable hooks to, and the other one is part of the main distributor shaft.

Jun 22, 2013 | 07:26 PM

jbakyy

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From: Graham NC

Quote:

Originally Posted by TimAT

There are 2 gears in there- one comes out by removing the coupling the drive cable hooks to, and the other one is part of the main distributor shaft.

It's part of main distributor shaft, how do you replace shaft?

Jun 22, 2013 | 10:29 PM

TimAT

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From: Gladstone MO

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The gear at the bottom of the distributor has a roll pin thru it. Drive that pin out with either a roll pin punch or a straight pin punch. Note the dimple on the gear close to the hole. It aligns with the tip on the rotor when you reassemble it. I think Lars has a paper on rebuilding the distributor with end lay specs.

Jun 23, 2013 | 09:35 AM

redrdstr72

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From: Lake Norman, NC

Quote:

Originally Posted by TimAT

Good advice! While you have the dist shaft out, be sure to check for play in the upper and lower bronze bushings. If worn, I'd expect to see wear on the shaft. New bushings can be found at your favorite restoration suppliers and maybe even your local auto parts house. Speaking from experience, I'd recommend a complete distributor rebuild, if you have it out of the engine, especially if you are replacing the shaft. There's not much more work to do a rebuild and I think you'll be happy with the results.

Jun 23, 2013 | 01:05 PM

lars

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From: At my Bar drinking and wrenching in Lafayette Colorado

There's more to it that just replacing the gears. If the crossgear stripped out, it has also trashed the mainshaft, as the other people above have noted. But the reason that the gears strip out is because the crossgear has worn itself into the housing thrust surface and hogged out a nice little counterbore right into the side of the casting. This causes the crossgear to jam itself into the worn area, lock up, and strip out. If you just replace the crossgear and mainshaft, you'll trash everything out again within 50 miles if you don't repair the housing damage. You have to custom machine a new thrust surface insert or a custom thrust button to correct this. It is also very likely that you need a new lower bushing, because all the metal filings from the stripped gears have gone down into the lower bushing area, and your bushing is now scored and trashed.

Lars

Jun 23, 2013 | 02:38 PM

redvetracr

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From: WI

Quote:

Originally Posted by lars

But the reason that the gears strip out is because the crossgear has worn itself into the housing thrust surface and hogged out a nice little counterbore right into the side of the casting.

Lars

wouldn`t a 71 distributor (if it is a 71 dist) have the factory installed plastic button??

Jun 23, 2013 | 08:49 PM

lars

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From: At my Bar drinking and wrenching in Lafayette Colorado

I get those distributors all the time where the gear has worn through the nylon button, hogged out the housing casting, and shelled out. The only thing remaining of the plastic button is the little stub of plastic stem still stuck in the hole... There are 2 causes of gear failure: Crossgear wear into the housing casting surface causing the crossgear to seize, and installation of one of those rediculous 90-degree tach cable drives, which increases the torque load on the crossgear to the point of failure. I've never seen a gear failure where one of these two issues has not been the cause.

Lars