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Huge 727 speedo gear?
#2764687
04/16/20 04:58 PM
04/16/20 04:58 PM
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Joined: Jul 2007
Posts: 1,682
Philadelphia
radar
OP
top fuel
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OP
top fuel
Joined: Jul 2007
Posts: 1,682
Philadelphia
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Howdy!
I swapped to a taller tire on my bigblock pickup truck and didn’t bother to mess with the speedo gear until recently- I was wondering why everybody on the highway was doing 50mph haha
Well I had a gps speedo app on my phone and I didn’t calculate the percentage but traffic was closer to 70mph. Definitely time to swap out to a gear that would match my new tire height with the 28” DOT drag radials I put on.
Ok so I have 3.21 gears out of a 70s ramcharger and 28” tire with an autometer mechanical speedo/odo. The axle/tire height charts say 31 tooth gear. I finally got around to swapping it out today and haven’t road tested it but the crazy thing is that the old gear was reeaaly close to correct if bot dead on, and when I pulled it it’s a 54!
I can’t even find a chart that has a 54 tooth gear and it looks like it would be for 13” tires and 1/8th mile gears?
What am I not seeing here? Sounds crazy right?
I’ll report back after driving it- just taking a break after rolling around working under the truck which I hate.
Last edited by radar; 04/16/20 05:07 PM.
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Re: Huge 727 speedo gear?
[Re: radar]
#2764734
04/16/20 06:37 PM
04/16/20 06:37 PM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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I'm a little bit confused. this might be too simple but if the GPS is showing the speedo to be 7% slow (for example) then you would want a speedo gear with 7% less teeth to speed it up
live every 24 hour block of time like it's your last day on earth
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Re: Huge 727 speedo gear?
[Re: radar]
#2764740
04/16/20 06:44 PM
04/16/20 06:44 PM
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Joined: Jan 2003
Posts: 29,652
Hamtramck, PA
Alaskan_TA
Fluffy Balladeer
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Fluffy Balladeer
Joined: Jan 2003
Posts: 29,652
Hamtramck, PA
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the crazy thing is that the old gear was reeaaly close to correct if bot dead on, and when I pulled it it’s a 54! At some point in time, newer gears no longer had the tooth count embossed in them, they went to the last two digits of the part number. If you count the teeth on it, there are not 54.
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