3.42

it is a little bit higher gear ratio which means higher speed and lower RPM's not much difference between the two

 

a 3.42 means the drive shaft will turn 3.42 turns to one full rotation of the wheel

same applies to any ratio 3.55 means shaft turns 3.55 times to one full turn of the wheel.

3.42 would have a higher top speed but less take off power than a 3.55 (not much difference between the two)

3.55 would have more take off power but a lower top speed at the same rpm

so when someone says a "higher gear" it means a lower number .......a "lower gear" would be a higher number

 

3.42 has less leverage than a 3.55.

depending on how the entire driveline is set-up with transmission gears and tire size, you can do a LOT of changing of final gear ratio at the ground.

 

You would never notice the difference between a 3.42 and a 3.55 ratio.

 

You can download the Cummins Powerspec program here: http://www.powerspec.cummins.com/site/home/index.html

It will give you engine rpm at a given speed for every combination of components(transmission, tires, rear end ratio) you can imagine.

They used to have a page where you could do it online but have changed their site, so I don't know if it is still available.

 

Except a 3.42 would be about 50 less rpm on the engine at the same road speed compared to a 3.55.

 

If you have tall rubber (11R 22.5), you can change to lo pro tires and change your final gear ratio by 50 rpm as well which will give you a little better pulling.
BTW, 3.42 is a Rockwell... ratio 342 358 373 390 391 410 411 430 433 488 529

 

Change tire size.....

poor mans gear change.

 

Costs more to change 8 good quality drives than change gears so I don't think that qualifies as a poor mans gear change. Sometimes a tire change is a better option also.