1955 Ford speedo driven gear.

Sid

Sid

Well-known member
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?
 
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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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.
 
Daves55Sedan said:
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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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.
 
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.
 
55blacktie said:
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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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.
 
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.
 
Jwawhite said:
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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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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