Gear Swap
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Senior User
Joined: Jan 2017
Posts: 183
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Cool. Keep us posted here. I talked to my dealer Friday night and he's going to have an estimate for me next week. I was thinking 4.10's because with the larger tires they would put me right back where I was with the 3.73's and the smaller tires. What made you decide on 4.30's?
Senior User
Joined: Sep 2018
Posts: 157
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I decided on the 4.30 based on the advice of other members. Some even recommended 4.56 but it might be a long time until anyone makes them for the M275 rear end. Currently, I have 245/75r17 tires. If I go with taller tires, it will bring it down to a 4.10 ratio. My truck does fine towing with my current gears/tires, I just want it to be better off the line and holding gears on hills.
Senior User
Joined: Oct 2017
Posts: 111
Likes: 1
I’m on 37s and went from 3.73 to 4.88, which is about 4.50 effective ratio. I wouldn’t waste money going from 3.73 to 4.30. Go to 4.56 or 4.88, it’s not as big of a jump as it sounds. Better yet, get on some gearing calculators and do some math and see where you land with the different ratios. It’s an expensive swap so do your homework.
New User
Joined: Nov 2017
Posts: 16
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From: New Haven, CT
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Logistics Pro
Joined: May 2017
Posts: 3,523
Likes: 483
From: Southern OH
Going from 3.73 to 4.10 isn't enough to justify the cost on a gas engine. I would go with 4.56s if it was me.
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Logistics Pro
Joined: May 2017
Posts: 3,523
Likes: 483
From: Southern OH
Yes you will, but with 38s I would consider 4.88 or even 5.13 gears.
Mountain Pass
Joined: Jan 2018
Posts: 202
Likes: 3
From: Rancho Cucamonga
Might be a stupid question but gears/re-gearing is foreign territory to me. If I re-gear to a high ratio and delete the truck (thus added HP/torque), will the gears support/last this?
Logistics Pro
Joined: May 2017
Posts: 3,523
Likes: 483
From: Southern OH
So you have a diesel then I assume? That's changes things, diesels have a lower rpm operating range so they need higher (numerically lower) gears than a gas engine. I would do the power upgrades first then decide if you need to regear or not. I wouldn't run any lower than a 4.30.