Torqueflite Speedometer gear choice

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prorac1

prorac1

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Were currently rebuilding the 727 for our 63 valiant build. And I started searching for the correct gear for our setup.

3.73 gear. 245/60/15 tire (26.57).

Falls around 37 tooth on the charts I've found.

Where's a good place to purchase?

We currently have a 30 tooth.

Thanks. Eric and Jason
 
On a side note be sure you have the right tire dia for your calcs. GPS & some math is the best. in a parking lot getting a rear tire valve stem at 6 0'clock then rolling the car forward in a straight line till the stem is back at 6 0'clock & tape measure that distance (~8 ft) then divide Pi (3.1416) into that # for the actual dia is second best & putting something flat across the top of the tire & measureing down to the ground for diameter is 3rd (but I admit the third method did work for me) but my OCD is always on me. If it ain't dead on a whole # I would go to the next smaller tooth count (tickets ain't cheap). & something I remember from drag racers is that a tire can grow at speed.
 
Just go by the chart. There is no point in getting real fancy measuring tire roll-out, tire growth at speed (what speed, 200 mph?) etc... when in the end we all know that the speedometers are not too accurate to begin with, and that you'll always end up "rounding off" to the closest gear anyways.
 
TrailBeast said:
Larger? :D
Click to expand...
in my post I went back & forth on which way (larger or smaller) was right for my line of thought & I'm thinking a smaller one would make the speedo turn faster, overdriven (read higher) & say for instance, show 68 when you are actually going 65 so you would then slow down a bit as opposed to a larger tooth one that would turn/read slower & show 65 when you are actually going 68 & you would think you were legal when you're not.
69_340_GTS said:
Just go by the chart. There is no point in getting real fancy measuring tire roll-out, tire growth at speed (what speed, 200 mph?) etc... when in the end we all know that the speedometers are not too accurate to begin with, and that you'll always end up "rounding off" to the closest gear anyways.
Click to expand...
I always get fancy/complicate things, YMMV.
 
Rapid Robert said:
in my post I went back & forth on which way (larger or smaller) was right for my line of thought & I'm thinking a smaller one would make the speedo turn faster, overdriven (read higher) & say for instance, show 68 when you are actually going 65 so you would then slow down a bit as opposed to a larger tooth one that would turn/read slower & show 65 when you are actually going 68 & you would think you were legal when you're not.
I always get fancy/complicate things, YMMV.
Click to expand...

And you are right (smaller gear turns faster and shows a higher speed)
Mine shows 5 under my actual speed, but I know that and account for it.
 
it is simple but it is a brain twister. I think what you said is a good plan, to know how much error you do have so in special circumstances (such as a cop in the rear view) that you can act accordingly & whichever tooth count got me the closest (above or below) that that would be maybe a good choice/or go with the smaller one.
 
That's kind of where we're at with this. Trying to get it "in the ballpark".

A 37 tooth should be close enough for spit balling.

An electronic speedo and a laptop would be handy right now. Lol

Thanks. Eric L
 
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