40 pickup stock

[Walt Dupont--Me.]

Mathematician. Boy, is that a long word. A friend has a 41 pickup, all stock. 3 speed trans. 16in tires. He just installed 3.54 gears, The question for that big math word. What RPM should that stock engine be turning at 60 MPH? I know some of you guy can figure it out. Thanks Walt

[Andy]

The number I found on line for the tire dia is 28.8". If that is right, the engine would be at 2480 rpm at 60 mph.

[39topless]

Will your bud need to recalibrate his speedometer after changing gears (guessing from 4:11?), if he stays with the stock size tires?

[Mart]

Walt, you didn't state what size of 16" tyre.
6.00s = 2548 rpm
6.50s = 2461 rpm
7.00s = 2378 rpm
7.50s = 2302 rpm

All at 60 mph with 3.54 gears and 1:1 top gear.

I used this (right hand table)

http://www.wallaceracing.com/calc-gear-tire-rpm-mph.php

6.00s = 28 in
6.50s = 29 in
7.00s = 30 in
7.50s = 31 in.

Mart.

[38bill]

Originally Posted by 39topless

Will your bud need to recalibrate his speedometer after changing gears (guessing from 4:11?), if he stays with the stock size tires?

Just needs to change the driven speedo gear if required. Speedo stays the same.

[Walt Dupont--Me.]

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Thanks guys. My friend came today and we hooked up a tack and it was running close to 2500 rpm at 60mph. He just bought the truck and was disapointed with the 4-11 gears. It was more fun to drive today. He did get the speed ometer gear and it's right on. Thanks guys. Walt

[41panelmark]

I swapped out the 4:11's in my panel with 3:54's and what a difference that made on the highway. Can be an issue if you are going up hills though.

[Seth Swoboda]

If you change the rear gears to 3:54 you should also swap the transmission cluster and main shaft to 29/15. You do not have too but this will help with starting from a dead stop and will be easier on your clutch.

[adileo]

Originally Posted by Walt Dupont--Me.

Thanks guys. My friend came today and we hooked up a tack and it was running close to 2500 rpm at 60mph. He just bought the truck and was disapointed with the 4-11 gears. It was more fun to drive today. He did get the speed ometer gear and it's right on. Thanks guys. Walt

Walt is it 6 volt? How did you hook up a tach? I was told that a tach on my 6 volt 39 was not possible. With stock ballast resistor / skip coil.

Thanks Andy

[39portlander]

Walt, you tell Ken I will be up and we can see who gets to Ainslies first from your dooryard, I'm bet'n on my 3:54's. Scott

[Tim Ayers]

Originally Posted by adileo

Walt is it 6 volt? How did you hook up a tach? I was told that a tach on my 6 volt 39 was not possible. With stock ballast resistor / skip coil.

Thanks Andy

You can always get one of those cheap digital ones that wrap around a spark plug wire. I have for my motorcycle. It works off a watch battery. Amazon sells them for about $15. Hide it in a spot that only you can see. Bonus is when the motor isn't running, it's a Hobbs meter as well.

[Barlea]

Back in the late sixties, I put a tach on my '53 Customline Coupe, the only change necessary was the bulb to 6V and it seemed reasonably accurate as I recall. Tough to get it over 4000, but it sounded good trying.