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Thread: 3.42
- 07.20.2012 #1Bobtail Member
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3.42
can anyone tell me what having a 3.42 Ratio truck means compared to a 3.5 ect?
- 07.20.2012 #2Road Train Member
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it is a little bit higher gear ratio which means higher speed and lower RPM's not much difference between the two
- 07.20.2012 #3Road Train Member
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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
- 07.20.2012 #4Trained Monkey
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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.
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- 07.21.2012 #5Road Train Member
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You would never notice the difference between a 3.42 and a 3.55 ratio.
- 07.21.2012 #6Light Load Member
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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.
- 07.22.2012 #7
- 07.23.2012 #8Medium Load Member
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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
- 07.23.2012 #9
- 07.23.2012 #10

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Sometimes a tire change is a better option also.

can someone tell me about what my truck is worth just a...
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