Speedometer gear
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More Turbo
Joined: Jun 2005
Posts: 561
Likes: 67
From: Sandpoint, in north Idaho
Speedometer gear
My '49 F1, stock 6 cyl., 3 speed:
the speedometer reads low, maybe 2/3rds of actual speed.
At Dennis Carpenter I see they show gears with 19,20,21and 22 teeth.
Maybe I am running the wrong one, or?
Any idea which one is correct?
Thanks, Brian
the speedometer reads low, maybe 2/3rds of actual speed.
At Dennis Carpenter I see they show gears with 19,20,21and 22 teeth.
Maybe I am running the wrong one, or?
Any idea which one is correct?
Thanks, Brian
Fleet Owner
Joined: Jul 2004
Posts: 27,297
Likes: 1,059
From: NM
You're reporting a 33% difference; the difference between the extremes of those gears doesn't come close to that. I'd suspect your speedo needs a good clean and lube. There is a little wick on the back of the speedo, right where the cable connects, that is for oiling, try a few drops there, but it is internal where it likely needs lube.
Are you running tires close to stock? (diameter)
Are you running tires close to stock? (diameter)
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More Turbo
Joined: Jun 2005
Posts: 561
Likes: 67
From: Sandpoint, in north Idaho
Yes stock 16" tires. I will check the lube;just thought there would be some erractic behavior with the dial like when the cable needs lube.
The speedo has been like this since last resto and really isn't a big thing as it is not a daily driver and I don't push it.
Sounds like I need to pull the cluster (a winter project);need to do that anyway as there is some dust flecks that somehow showed up right after installation. Ugh!
Thanks, Brian
The speedo has been like this since last resto and really isn't a big thing as it is not a daily driver and I don't push it.
Sounds like I need to pull the cluster (a winter project);need to do that anyway as there is some dust flecks that somehow showed up right after installation. Ugh!
Thanks, Brian
Fleet Owner
Joined: Jul 2004
Posts: 27,297
Likes: 1,059
From: NM
You're right, if it were purely a cable problem you'd see it jumping around. Mine failed right at 99,992 miles because the drum that moves the needle (which isn't directly connected to the cable) wore out its bearings, and started hitting the drum connected to the cable. It would be the only time I saw 85 mph on it! 
It's really tough to open the unit up without ruining the chrome trim ring.
It's really tough to open the unit up without ruining the chrome trim ring.
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Post Fiend
Joined: May 2008
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From: Poway, Ca.
Ok well lets confirm that you have the stock rear end in the truck too. If so then you shouldn't even be able to get it up to 65 (maybe downhill, with a good wind at you back, at 3500rpm). 2/3 of that would be 32mph!!!!!!
2/3 of acutal speed is quite. My 51 with a 2.80 rear has a speedometer that reads exactly 10 MPH slow at 70 mph.
Curious, how are you clocking your actual speed?
2/3 of acutal speed is quite. My 51 with a 2.80 rear has a speedometer that reads exactly 10 MPH slow at 70 mph.
Curious, how are you clocking your actual speed?
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More Turbo
Joined: Jun 2005
Posts: 561
Likes: 67
From: Sandpoint, in north Idaho
Julie, yea stock rear end. Clocking actual speed by traffic and also based on the speed of someone else in a newer vehicle. Figure that at about 55 mph it shows 40. It is not a huge issue as I only drive it into town and back, about 7 miles each way and that only 20 to 30 times a summer. Just would like to correct it if not a big deal; oh and of course I need to remove the dust behind the glass that showed up after installation as my son pointed out! brian
Post Fiend
Joined: May 2008
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From: Poway, Ca.
As Ross mentioned, the chrome ring holding the glass on is attached at four places where the edge of the crome ring is bent and tucked under the speedo housing. You just need to "CAREFULLY" pry out two of those crimps on the same side to get the chrome ring off to clean the glass. Be careful when the chrome ring comes off everything falls out - including the glass.
You may be able to get close with a driven gear change. I'd take it to a speedometer shop and have them put it on the dyno to give you an accurate reading and they can fix it either with gears or a reduction box. Should cost about $35.
You may be able to get close with a driven gear change. I'd take it to a speedometer shop and have them put it on the dyno to give you an accurate reading and they can fix it either with gears or a reduction box. Should cost about $35.
Laughing Gas
Joined: Jul 2003
Posts: 1,224
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From: scotia. NY 12302
actually i'm just comparing the two to make sure the gps is accurate. it is interesting that i replaced my speed gear (HD 3speed, metal gear) with one with one more tooth (or less, can't rem) and have 2.25-75 on the rear and the stock speedo agrees within less than 1mph with the gps. i have no idea if the speedo was acc with the old gear and the 2.25-75's, just assumed it was.
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