RPM on 3406 B cat

it aint gona hurt it at that rpm. just run her till she blows!!

 

just bump the gate it wont leave dents!!

 

I need help I'm running a 3406b cat with a 15speed and 3.70 gears and at 1500rpm I'm running 60mph I stay in Texas Louisiana and Mississippi so no big hills what gear ratio do I need to be running id like to be 70 to 75mph at 1500rpm

 

What tires?

 

First a little info; RTO16915 has overdrive ratio of .79
it appears you run Low Pro 22.5 rubber

You need tire size revolutions per mile
11:24.5 = about 475 Rev Per Mile Average
24.5Low Pro & 11:22.5 = about 500 average
22.5 Low Pro = about 510 average

The formula you need is
(rpm X 60) divided by (rear end ratio X trans ratio X tire rev per mile)
in your case (1500 X 60) divided by (3.70 X .79 X 510)
90,000 divided by 1,490.73 equals 60.3 MPH

3.55 will bring you to 62.9 MPH
3.36 66.4 MPH

Now you have the info to play around with tire size or rear end ratio or trans swap (13 speed has final ratio of .73) tire manufactures have rev per mile info on their web sites.

 

Knowing the torque curve I wouldn’t be pulling a narrow bearing B model at 1300rpm.

 

Depending on what serial# B you have the governor may have a different spring than the others youve ran and originally be a 1800rpm motor with a different governor spring that originally was meant to cut fuel back sooner...you would need to have the set point rpm checked or just put a new purple stripe spring in it and set it up to turn 2200-2300rpms in neutrel no load rpm. Like Smokin Cat said you dont want to be pulling hard with a narrow rod bearing B model at 1300 very often or ever really!! expecially for any extended periods of time.

 

CATS like lower rpm they get good mpg there too there built for that look at the torque charts that tells your were u wanna run try to balance torque and power. I suggest between 1400 to 1600 rpm running down the road and 1400 to 1500 to shift and with a c15 you can shift even lower like between 1300 and 1500 thats the way my father does he drives a Cat on the weekends lol all the dpf truck wana try to race to the plant to get loaded we can run with em at about half throttle and thats with 3.65 rears tires im not sure and a 1.4 million mile cat that has no rebuild.