3.42 rears to 3.58

Not much maybe 370 or 390 good luck somebody more knowledgeable Will be here soon !

 

It is Not worth turning the wrenches on that one. Very little difference with those ratios. You can change them if you really want but the truck is gonna feel the same when you start tugging a hill.
Your 13 speed is a good trans ratio, what is your tire size? If your up on 24.5 high rubber and you swap those rears and go to lo pro 24.5 tires then you would begin to see a difference. But just that swap on it’s own isn’t gonna do much for you.

 

How about you tell us what kind of truck, what kind of engine, what the current rated power is, how many miles on it, etc.

I find gearing doesnt always make up for a lack of power. For example:

Last year I was driving a Volvo with a 12.7 Detroit set at 550hp (at the rear wheels) a 13spd and 2.79 gears.

I have been running a 2010 KW T660 with an ISX set at 450hp, 13spd and 3.55 gears. While the 15L engine pulls well with the deeper gears. I lose speed and am considerably slower up hills than the previous set up.

Fact is, Ive actually become a fan of taller gears with a 13spd as I can run 8th direct to achieve the same rpm as with deeper gearing and running 8th over.

 

What tire size? Like others have said you won't feel it. Now if you went to 3.73 I think you'd be happy

 

I have 3.58's, and I climb pretty well. But I also have a 10 speed.

I'd think a 13 would work pretty good with 3.42's.

I'd guess it's probably about the same as my set up with the 10.

If you're hauling near gross on steep hills, I run the western US, even guys with big motors aren't going up those hills all that much faster than I am.

 

I have 13 with 3.42 and have no complaints. You just need a stronger engine

 

Dont waste your time and money. That change will not gain anything really. Better to look into what you can do on the ECM tuning before doing hard changes to the equipment.