3.55 and 3.58 ratio difference

I cant see the difference between even 3.58 & 3.36.

 

You won't see a difference.

 

3.58 pulls better than 3.36, thats obvious.

 

3.58 are usually rockwell rears gear sets and 3.55 are Spicer/Eatons gear sets. Take it you are running LP tires both are so close it wouldn't matter. I prefer spicer/eaton over the Rockwell had better luck with them wheel seals and bearings and power divider. Both trucks I had that had rockwells ate wheels seals like candy. 1 wheel seal in 1 mil mi on eaton. Rockwell does make a better steer axle.

 

First off, anyone that says one gear ratio pulls better then another is lieing. There are way to many variables to know anything for sure off that. Tire size, engine type and trans type all factor in as well. The big difference is engine and trans. A 06 cat gets peek mpg at 1200 rpm but doesn't loose much till you hit 1400. You want to set up your truck to cruise in that window. Now a Detroit s60 likes 1400 much better and can go up to 1600 easily. Cruising at 1200 would be lugging the engine a little and reduce mpg for a detroit.

Now, the difference between 3.55 and 3.58 isn't much, but a 58 will go slower for a given rpm. If you have a 13 speed trans and normalish tire size on a Detroit, a 55 will get you 63 mph @ 1400 rpm while a .58 will be a few mph less. Obviously for a cat, if you want to go 65, it would put you over 1400 rpm with both a 55 or a 58, so you have the option of larger tires or higher gearing to compensate.

As for how they pull...gear ratio doesn't matter aside from first gear. A high ratio in a low gear is the same as low ratio in a higher gear. As long as you can down shift, you can make up for a ratio. the ratio does affect your off the line, but if you have a 9 or 13, you can always use low when you need it.

I'd probably recommend the .55 to give you a little more high end speed and drop your cruise rpm a little. That being said, to give a real recommendation, I need to know trans, engine type, and ideally tire size.

 

Its all in theory. In practice 3.58 and up are better pulling trucks coz on every given gear you apply more torque to the wheels.

 

But down shift one gear and you have even more tourqe. And that will get you a lower top cruise speed if you want high mpg.

 

Assuming you are talking about swapping 3.58's for3.55's on a truck without changing anything else (or visa-versa) there won't be any measurable difference between the 2, you are talking about 0.03 of a rotation.

 

Again, its all in theory. I drove 3.58 and now 3.36. All I can say mileage is similar, but 3.36 is horrible climbing a hill. In the next topic Oram has 9mpg on 3.06 against guy with 3.58 with 8mpg.