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Discussion Starter · #1 ·
I just realized my truck has 3.08s in the rearend, I would like to put so 3.73s in it but I would like to know a few things. How did the fuel economy suffer from the change. What size rearend do these trucks have. How much seat of your pants did it pick up? Ive ran 3.73s in a few cars but they have been older and gas guzzlers anyways, but I drive my truck everyday 40 miles each way and would like to still keep my milage pretty good.
 

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just a senior...
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how tall is your tires, factory, and you plan to retain factory? If you ever go bigger, change...even swapping to deeper gears can NET you power, and better gas mileage.
 

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how tall is your tires, factory, and you plan to retain factory? If you ever go bigger, change...even swapping to deeper gears can NET you power, and better gas mileage.
Also do you have a 4 speed or 6 speed trans? I believe a 4 speed with 4.56s is fairly close to a 6 speed with 4.10s.
 

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Discussion Starter · #8 ·
I have the 6 speed tranny but I think 4.10s would be too much. Its a street truck and I mostly want to do it for performance gains but not ruin my gas milage. What kind of gears should I look for? What type of rearend is back there, 14 bolt?
 

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Pro Installz
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With the 6 speed and stock tire I would say 3.73's would be nice. I have a set of gm 3.73 pull outs with less than 2500 miles on them that we pulled to pt in 4.56's. pm me if your interested
 

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There isnt a big difference between the 60e/65e/70e OD ratio and the 6l80e OD ratio 0.70:1 vs 0.68:1. There is a bigger difference when compared to the 4l80e which has a 0.75:1 OD.
The difference between the 60e to the 4l80e is less than 200rpm at cruise.

4.10 4l60e with 27" tires was too much for fast highway cruising. A 30"+ tire would be better.
3.73 is a good all around gear for lower tire heights.

The 6l80e has that stupid low 4.03: OD ratio which when it shifts to 2nd gear has more rpm drop than the4l60e did.

peace
Hog
 

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I have the 6 speed tranny but I think 4.10s would be too much. Its a street truck and I mostly want to do it for performance gains but not ruin my gas milage. What kind of gears should I look for? What type of rearend is back there, 14 bolt?
My bad, I thought you were going to lift it. Just assumed since thats why most regear.
 

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it's not fast enough
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i run 4:10s, even with the 5.3/60e set up i still got 19mpg on the highway with a 3600 converter and a huge cam. in city was a different story.
i run a stock 6L80e with stock converter and 4:10s they are fun. i get 17.5-18 with a lot of in city driving or 20-21 on the highway only. keep in mind im not where near stock
 

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what size of rear end and front end would my 2010 gmc sierra have? it's a 10 bolt but I'm not sure about anything else
 

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check your rpo code..
what size of rear end and front end would my 2010 gmc sierra have? it's a 10 bolt but I'm not sure about anything else
 

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i have a vortec max with a 4l70e a 16bolt and 4.10s and the 4.10s arent the greatest on gas. a great pulling/gas mileage/running at the track gear is a 3.73 hands down its the mid gear, but if u want all off the line 4.10 or 4.56s. im actually about to change my front and rear to 3.73s because of the all around use. but a 4.10 at 60 runs 2000 rpms and 3.73 at 73 or 74 runs 2000 rpms 10-15 mph difference which adds up quick i know it has between my two trucks.
 

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it's not fast enough
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i have a vortec max with a 4l70e a 16bolt
they dont make a 16 bolt. you have a 14 bolt, its the same rear end as the SS

i think the 2011s 10 bolts are 8.8 ringgear
nope, the 10 bolt is the same as the 8.5 from the 80-07 classic the "newer 10 bolt" from 99+ is a 8.625 to be exact and it only has a different bearing size but the ring and pinon is the exact same and so is the locker. a 8.8 is a Ford rearend if i recall correctly
 

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im runnin 4.56s with a 245/40/17. Kills me on gas tho.
 

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