rpm's n' gears

[jones]

rpm\'s n\' gears

i'm assuming some of you run your rigs on the freeway.what rpm range are you running with what size tires and what gear ratio.ex.)a guy told me he was cruisin at 4k at 55mph,w/4.10's and 33's w/ a 3spd auto.is that typical?

 

[dhdescender]

Re: rpm\'s n\' gears

@ 60mph I'll hit around 2650RPM with a 1:1 non overdrive 3 speed automatic, maybe a little higher accounting for TC slippage, this is with 5.13 gears and 42" TSL's.

This is with a Big Block Caddy motor that hates high RPM's

 

[big jimmy 91]

Re: rpm\'s n\' gears

http://www.florida4x4.com/tech/gearcalc.php
Go here and fill in the blanks to get all the info you need /forums/images/graemlins/thumb.gif

 

[87BrnRsd]

Re: rpm\'s n\' gears

4K is way to high to be running continuously. I am running 37's, with 4.56 gears, and a 700r4 overdrive transmission and at 65mph, I run about 2350 rpm's. Thats a pretty good rpm range to keep the engine and gas mileage happy.
-Harrison

 

[rjfguitar]

Re: rpm\'s n\' gears

I have 35's, 4.10's, th700, and a built 406 SBC. I cruise at about 1,700-1,800 RPM's. /forums/images/graemlins/whistling.gif

 

[Muddytazz]

Re: rpm\'s n\' gears

I'm running 4.10's and 33's with a TH350(standard 3-spd auto) and I'm running no where near 4K, more like around 2600

 

[jones]

Re: rpm\'s n\' gears

so a 4.10 and 31-10.5'swill be just peachy,huh? /forums/images/graemlins/thumb.gif

 

[trailblazer86]

Re: rpm\'s n\' gears

(MPH X Diff ratio X TCase Ratio X Trans Ratio X 336)÷ Tire Diameter = RPM

Therefore:
(55mph X 4.10 X 1 X 1 X 336)÷ 31 = 2444rpm

Try 80mph
(80 X 4.10 X 336) ÷ 31 = 3555RPM

Tire size can make a huge difference
Try 33"
(80 X 4.10 X 336) ÷ 33 = 3339RPM

Try overdrive and 31's
(50MPH X 4.10 X .70 X 336) ÷ 31 = 1555RPM
(80MPH X 4.10 X .70 X 336) ÷ 31 = 2488RPM

This is assuming direct drive. Torque converter slippage will add a few more revs.