Ratio 3.55

3.55s are better if you're running mainly acoss the flatlands, 3.70s for lots of mountain driving. 3.55's will allow you to do the same speed at lower RPM than 3.70s

 

Impossible to give you any meaningful info since we don't know what trans you have in the truck. If it's a direct drive trans, typically you will have a rear end ratio anywhere from 2.73 to about 3.10 or so. If the trans is a overdrive final ratio, (most likely) you will typically have a 3.55 or higher. The goal is to have the engine running in it's sweet spot at road speed in high gear. The sweet spot on an engine is usually somewhere in the 1400-1550 range depending on the particular engine, and is usually the spot where the torque peaks on the engine.

 

^^^ You got that backwards boss, a overdrive trans works better with 3.55 or lower gear lets say, depending one engine and torque output and a direct drive is better off with a taller gears like a 2.79, but thats uncommon now a days.

Tell us what trans you have, i had 3.70s in my Pete and they were great for pulling steel trains in MI but they sucked for west coast running. I say, for no matter what you are doing, with a 13 or 18 speed 3.55s are perfect but if you have something like a 10 speed i say go with the 3.70s due to bigger rpm drop when shifting. Basically the higher the number the higher the rpms when driving and the slower the speed.

 

You are correct, I screwed the pooch on that one, but it's late at night, I've been up all day, and I still have to drive to Green Bay by morning.

But, I will correct it. LOL!

 

Dang! Were practically neighbors too, its no problem....... If you ever see a white and black W900 with a spread axle reefer running down 94 thats me, i usually load at welches in Lawton....... Sorry for the off topic.

 

Myself, I'm an white and orange Mack Vision with a Bulkmatic tanker behind me.

 

what those numbers mean is... for example 3.55, the drive shaft will turn 3.55 times for every one time the axle shaft spins. 4.10 would be 4.1 times for every one. The more times the driveshaft turns the more torque multiplication you get to the ground so it will be easier to get up to speed. but it also means when you up to speed your motor will be turning higher rpm's with the 4.10 than the 3.55. the proper way to write t is 3.55:1 by the way but it just gets shortened up to 3.55.
so you need a calculator t be able to puch in all your gear ratios, tire size and spped to come up with rpm and you want your cruising rpm to be in the "sweet spot" for your motor.

Now if you really want to get confused.. the 3.55 is a considered a "higher" rear end than a 4.10 even though it is numericlly lower.

 

If you go to roadranger.com, there is a road speed calculator in the "tools" section. Its pretty neat. You select your transmission and tire size, and it will show a chart of rear end gear ratios with the road speed matched to your setup.

 

So does http://www.powerspec.cummins.com/powerspec/doc/site/gearing/gearing.htm