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I got my 4.10s in last week and just completed the 500 mile break in and oil change, I am very pleased with my choice so far, I really think 4.56 would have been too much, and I wouldn't be able to get traction anywhere. Also my MPGS, jumped by almost 5, I am getting a custom tune Wednesday.


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Good to hear, I have a tune already, which is another reason why I'm going with the 4.10's. Pretty sure I'll be more than happy with them and the BB tune together.

Where did you get your gears from? I was just looking at getting these...

http://www.ronsmachiningservice.net/gear-install-packages/chevy-truck/1999-on-4wd-1-2-ton-8-6-8-25/2009-2013-chevy-4wd-gm-8-6-8-25-ifs-master-install-4-11-gear-pkg/
 

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I got mine off Amazon- motive gear
I have the 14 bolt rear axle and 8.25 front IFS, the one in your link is for the 10 bolt.


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I got mine off Amazon- motive gear
I have the 14 bolt rear axle and 8.25 front IFS, the one in your link is for the 10 bolt.


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Ha, to be honest I just assumed that I have the 10 bolt.....which is why I posted that.....I'd obviously double check before I order.
 

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well i just went with 5.13 gears front and back and detroit trutrac and im running 38X15.50x20 tires. getting installed next week hopefully
 

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That will be a fun ride for sure.
 

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Wish they made 4.30 for mine


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Really wish they would come out with a solution for these 14+ trucks. I ended up with 3.08 ratio and still on stock tires, I hate it. Getting the truck tuned tomorrow, so that should help, but I'd like to go 4.10 before I pickup some 33's. Just playing the waiting game for now.
 

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What solution? Did you not know what gears you had before you bought it? The solution is deeper gears and a retune.
 

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What solution? Did you not know what gears you had before you bought it? The solution is deeper gears and a retune.

There's still no direct gear swap available for these new trucks with the 3.08 ratio. I've heard from various people that Yukon is working on coming up with a solution for that. The story on the 3.08 is when I bought my truck I knew these had more horsepower than previous trucks and the truck I bought was the last one on the lot with all the options/package I was looking for. I don't tow very much so at the time I figured the additional power and a tune would offset the tall gear ratio. During the test drive it felt fine, but I screwed myself because I test drove around the same time rush hour was picking up. Needless to say I got a feel for it and it felt fine, but after buying and actually spending some time behind the wheel the 3.08 have to go. I got a pretty good deal on it as it was a leftover 2014 they were trying to get rid of so in the end I still love this truck, but at some point I'm going to swap for 4.10s

**Edit - I actually just got my tune today so I'm pretty stoked to get it up and running
 

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You can swap the gears. You will need a new carrier or carrier case, and some of the bearings will need to be sourced elsewhere. Kind of a pain, but can be done.
 

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I see there are a ton of replies to this topic so I do apologize if someone has already shared this link. I used this site to compare gears. Just punch in the gear ratio tire size speed and trans ratio and it will give you the rpms.http://www.csgnetwork.com/multirpmcalc.html

For what its worth to anyone reading I have a 2000 5.3 4wd 6 inch lift with 285/70/r17 (32.8inch) and I went with 4.30s. I live in the mountains a drive lots of hills and tow a bunch too and these gears are about perfect for me. If you drive lots of 70mph+ hugway go 4.10 or lower.
 

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some good stuff here, changed my 3.42 to 4.11 in my garage. pretty easy considering how much the stealership and other garages wanted to charge.
 

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New Gear = (Target RPM * Tire Size)/(Cruise Speed * 420.38 * OD)

4.24 = (2500 RPM * 0.8 * 35”)/(70 MPH * 336.3 * 0.70)
I looked through as many messages as I could stand but couldn't find the answer to this. In the Method 2 formulas (quoted above), the generic formula has a value (420.38) that is different from the example (336.3) below it. What is that number? If it's some type of correction, then it should be a constant. If so, which one is correct? If it's a variable, what is it?

I've noticed several people using one or the other and then commenting about their odd results. Using those two numbers would produce markedly different results. Before I start buying gears for myself, doesn't anyone know what the correct answer is for that value? Thanks in advance.

Again, I apologize if this was covered somewhere in this thread but I didn't see it.
 

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Putting "Sticky" in the title is bold, but this information is needed. In an effort to curve or possibly stop the endless barrage of “What Gear?” threads that pop up daily on this page, I am providing some simple calculations to help in the gear selection process.

The Quick and Dirty:

Your have increased the size of your tire, what gears should you buy?

Old Tire Size – 31”
New Tire Size – 35”
Current Gear Ratio – 3.73

New Gear = (New Tire Size / Old Tire Size) * Current Gear Ratio

4.21 = (35/31) * 3.73

Since you cant buy 4.21 gears, it would be advised to purchase 4.56 gears. It is advised to round to the next lower ratio to account for increased rolling resistance, and reduced aerodynamics from being lifted.

Method 2:

This method is a bit more favorable as it takes into account a target RPM in your engine's power band for a given cruise speed.

New Tire Size – 35”
Target RPM – 2500 RPM
Trans. Overdrive Ratio – 0.70 (4L60E)
Highway Cruise Speed – 70 MPH
Correction Factor - 0.8

New Gear = (Target RPM * Tire Size)/(Cruise Speed * 420.38 * OD)

4.24 = (2500 RPM * 0.8 * 35”)/(70 MPH * 336.3 * 0.70)

In this instant you would use a 4.56 gear. Note that this calculation has a correction factor that provides a little insurance for passing, hills, towing, hauling, etc.. I used 0.8 which should be about right for most engines. If your engine makes A LOT of torque at your target RPM, you can use corrections factors of 0.7, 0.6, 0.5 etc... Also, this calculation assumes that a lockup stall converter is used in automatic transmission applications.

Here is a good link with some very good calculators. Bear in mind that no corrections are applied with these calculations.

http://www.bncoffroad.com/ratio/

EDIT: Method 2, see post 10.
I have a 07 Silverado lifted 8” on 35”. G80 8.6 axle, i had 3:73 from factory and decided to go up to 4:56. I put
GM 8.6" Detroit / Eaton True Trac - 4.56 Ring & Pinion - Bearing Kit - 30 Spline. I heard if you just replace the gears without rebuilding the whole diff, it’s very easy to destroy it cause the stock parts don’t like the new gearing. Is it true? I’ve had them rebuilt for about 3 months and have driven it hard a few times and I have no problems.
 
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