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Technical Info: 3rd Generation: DRIVETRAIN Technical discussion of third generation (2003 - 2007) engine and drivetrain questions, solutions and upgrades.
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Old 08-11-2021
patleon patleon is offline
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Default 4.10 to 3.42 differential gears

I have a 2005 Dodge quad-cab with 35" tires, 4.10 gears and an NV5600 transmission. I'm considering changing from 4.10 to 3.42 gears to increase MPG since I don't tow much. That way I can use overdrive when traveling empty or pulling a light load and if I need to pull something heavy I can use 5th gear. Rather than have somebody change the gears I'd like to find a complete set of differentials with 3.42 gears and swap them out myself. What years will fit my 2005?
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Old 08-12-2021
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6 from 1, half a dozen to the other. I wish I had 4.10s, but I use my truck for hauling and towing. If I need better fuel mileage for putting around, I drive the Subaru. It's a balancing act between what and were you use it versus how you use it. Tire size and gear ratios change engine RPM obviously. The trick is to not load the engine by changing one or both. Getting the RPM down may or may not help your fuel mileage, and I specify your. If you wind up lugging it all the time, fuel mileage will go down.
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Old 08-13-2021
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If you throw you numbers into a calculator, it looks like you will drop your RPM's by about 300 at 65 mph (Assuming 35 inch tires, .73 overdrive, and 65 mph)

https://purperformance.com/p-29669-rpm-calculator.html

Whats your average MPG now? A set of axles would not likely come cheap unless you get a smokin deal, it would take a long time to offset the cost for a small MPG gain.

If it is something you want to do, I think you might want to at least get an estimate to have the ring and pinion themselves replaced, it may end up being cheaper than a set of axles, and you could have them throw a locker or limited slip in while you are at it.

03-09 should fit, I think the front suspension changed for the 4th gen, so I don't think the front axle would work from 10 and up.
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Old 08-13-2021
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I am generally not a fan of 4.10's.
Had them in my 96, but it was strictly a tow truck...grossing over 25k#
Worked pretty well for that I guess.
I thought it was 4.10 or 3.55..??
Had the 3.55's in my 99 and it was great!! 2000 RPM at 70 MPH and all day long!
Don't know how much the 35's would change that.
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