1957 Tachometer drive gear removal from distributor

schrobird57

schrobird57

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Joined
May 26, 2022
Thunderbird Year
1957
In looking into why the tachometer is not working. I pulled the tach cable at the tach gage. It did not turn when the car was running. So next, I removed the tach cable from the distributor housing. The drive gear did not come out with it. In looking at the end of the tach cable it looks like there is a nylon piece with rough edges like it broke off from what plugs into the drive gear. Using a mirror and looking into the bore where the drive gear is I see what looks like the other end of a nylon piece. I tried to get a small needle nose into the bore to remove it but I just can't get a grip on it. I can't seem to find any photos of what that interface is supposed to look like.
Is the nylon piece part of the cable or part of the tach gear?
Does anyone have any ideas of how to pull the tachometer gear without removing the distributor?
Thanks for any help. I'd rather not have to pull the distributor if possible.
Curt S.
IMG_2654.jpgIMG_2655.jpg
 
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An original metal driven gear at the distributor end of the Tach cable ltach cable driven gear.jpgooks like this one.
 
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Looking at your pictures I don't believe you have the correct parts. You can buy a new tach cable and I believe the drive gear from 55-57 T bird vendors. Doesn't sound like you want to pull the dist. This is extra work but you should be very close to where you started. Take valve cover off where no. 1 cyl. is located. Turn the engine over till no. 1 intake valve closes and timing mark is near TDC. Pull the dist cap take a file and mark on the dist. where the rotor is pointing. Now take a center punch and make a mark on dist and engine where they line up. Now pull the dist and you will have to get the junk out. Because of the helical drive gear on the bottom of the dist. you will have rotor a little to the left to get it back in alignment.
 
I agree with sre, I don't remember the tach driven gear being made of nylon, but I could be wrong. CASCO sells the driven gear and it looks to be a metal gear, they also sell the complete tach cable without the driven gear.

Tach 1.jpg

Tach 2.jpg

If you can't remove the broken broken driven gear from the distributor housing, than you will have to disassemble the distributor. I have overhauled quite a few of these distributors and it is easy to do.

doug7740
1955 Thunderbird Blue

Tach 3.jpg
 
Thanks all for your responses... very informative. It definitely doesn't look like the photo from dmsfrr. And why anyone would think that nylon would have been a good choice of material is beyond me. Probably a crappy, ancient, aftermarket part. Thanks for the tips on keeping timing intact, I'm usually lazy, that way thinking pencil and Sharpie marks are good enough (until you accidently rub them off)
@doug7740 regarding your photo of the parts, is there a feature, (gear teeth) on the shaft that engages the gear as it rotates, it doesn't show up well in the photo?
This job will have to go on the back burner. To many higher priority jobs ahead of a non-working tach.
Thanks again!
Curt S
 
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Curt,

The tach drive gear slides on the distributor shaft and is pinned in place.

Tach.jpg

Below is a picture of the tach drive gear and pin before I cleaned it. And yes the inside of some of the distributors I've overhauled look this dirty.

doug7740
1955 Thunderbird Blue

Tach 2.JPG
 
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