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Old 05-31-2021, 12:26 AM   #1
Sid
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Default 1955 Ford speedo driven gear.

Working on a 55 Ford with a Fordomatic and 215/70/15 tires. 3.30 rear end. (approx 26.8 tall) The speedo. over reads. Probably about 7 miles faster. I know it needs a larger driven gear. It has a 19 tooth gear right now. I have no idea about the drive gear. And there is no way to see in the hole. The car appears to be completely stock. I would just like to get the speedo. closer then it is. It don't need to be perfect, just closer. Can I safely put a 21 or 22 tooth driven gear in the hole?
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Old 05-31-2021, 05:16 AM   #2
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Post Re: 1955 Ford speedo driven gear.

REFERRING THREAD - https://www.fordbarn.com/forum/showt...edometer+gears
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Old 05-31-2021, 08:10 PM   #3
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Default Re: 1955 Ford speedo driven gear.

CASCO has 20,21, and 22 tooth gears for 55. The TBirds used an angle drive, but I think the gears will fit a sedan cable. Ask them about this before you buy.


If I remember correctly, on tooth equals about 5 mph
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Old 05-31-2021, 09:42 PM   #4
Daves55Sedan
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Default Re: 1955 Ford speedo driven gear.

I would say it's not a big job to pull out a speedo driven gear from the trans rear extension housing. But you gotta be careful to pull it straight outta the hole. If the nylon gear teeth catch on the hole while you are pulling the cable out, the nylon gear will fall off the end of the cable and down into the bottom of the extension housing.
Never fear! if that happens, you can take a piece of spring-steel wire, (14 or 12 gage would be okay) and bend it into a shape like pliers with two prongs on the end. Poke the ends of the wire (facing down) into the hole and squeeze the pliers together and pick up the gear and pull it out. I've done it several times.
BTW, I am using P215-75R15's on the rear of my '55. They are closer in outside diameter to the original 670x15's, so I didn't need to change gears (although it might be a little off), there wasn't another modern tire manufactured at the time that came closer to the original O.D.
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Old 06-01-2021, 08:06 PM   #5
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Default Re: 1955 Ford speedo driven gear.

Quote:
Originally Posted by Daves55Sedan View Post
I would say it's not a big job to pull out a speedo driven gear from the trans rear extension housing. But you gotta be careful to pull it straight outta the hole. If the nylon gear teeth catch on the hole while you are pulling the cable out, the nylon gear will fall off the end of the cable and down into the bottom of the extension housing.
Never fear! if that happens, you can take a piece of spring-steel wire, (14 or 12 gage would be okay) and bend it into a shape like pliers with two prongs on the end. Poke the ends of the wire (facing down) into the hole and squeeze the pliers together and pick up the gear and pull it out. I've done it several times.
BTW, I am using P215-75R15's on the rear of my '55. They are closer in outside diameter to the original 670x15's, so I didn't need to change gears (although it might be a little off), there wasn't another modern tire manufactured at the time that came closer to the original O.D.

It's not my car. The speedo is about 8 or 9 miles an hour off. (over reading) I did pull the gear out and of course it did come off but didn't drop. I did order a 22 tooth gear. When I re installed the gear I put some grease on it so it wouldn't fall. This car has 215/70/15's.
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Old 06-01-2021, 08:16 PM   #6
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Default Re: 1955 Ford speedo driven gear.

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My 55 T-bird/w Fordomatic, OEM 3.31 gears, and 205/75R15 tires was about 10 mph fast at an indicated 65 mph, which is about 15%. I think it's common. Accessibility on the T-bird is really tight. One good thing about it is you should not have to worry about speeding tickets.
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Old 06-02-2021, 12:15 PM   #7
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Default Re: 1955 Ford speedo driven gear.

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My 55 T-bird/w Fordomatic, OEM 3.31 gears, and 205/75R15 tires was about 10 mph fast at an indicated 65 mph, which is about 15%. I think it's common. Accessibility on the T-bird is really tight. One good thing about it is you should not have to worry about speeding tickets.
That's true.. But is a little annoying being that far off. 2 or 3 mph fast isn't bad as it will give you a litter buffer zone.
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Old 06-07-2021, 12:18 PM   #8
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Default Re: 1955 Ford speedo driven gear.

Put a 22 tooth gear on and speedo. is about dead on.
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Old 06-08-2021, 12:54 AM   #9
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Default Re: 1955 Ford speedo driven gear.

Just a bit off topic, 56 Speedometer "Head": I've noticed on a '55 head there was an oiling port on the rear. The '56 does not. Question: do you spray lube inside the male speed cable screw area? My mph needle does not travel back to Zero when I stop.
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Old 06-08-2021, 10:14 AM   #10
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Default Re: 1955 Ford speedo driven gear.

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Originally Posted by Sid View Post
Put a 22 tooth gear on and speedo. is about dead on.
Oh no! Now you'll have to fix something else.
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Old 06-08-2021, 11:44 AM   #11
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Post Re: 1955 Ford speedo driven gear.

Quote:
Originally Posted by Jwawhite View Post

56 Speedometer "Head":

I've noticed on a '55 head there was an oiling port on the rear. The '56 does not.

Question: do you spray lube inside the male speed cable screw area? My mph needle does not travel back to Zero when I stop.
How difficult is it for you to remove the speedometer head? I am asking as it is most likely dirty and gummed. You would need to clean and re-oil.

If she doesn't zero after that service, you would need to send it to a repair shop.
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