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Does anyone know a good shop in the Nashville Tn are that does diff gear swaps ? I pull a 26 foot camper loaded weight is about 7k . I have 3.08 gears and i want to swap to a 3.73 or 4.10 . Anyone have 4.10 gears ? What MPG are you getting ? 

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What kind of truck do you have though?


The right choice for gear ratio can depend on what engine you have and what transmission you have too. Like a 6 speed auto could use the 3.73's better than a 4 speed auto.


You can also plug this information into a transmission/rpm calculator so you can get a good guesstimate of what your new highway speed rpms are going to be.


Like my previous truck was a 5.3/6L80e with 3.42's, I could get 20-22mpg on the freeway if I wanted too. It was turning about 1600-1700rpm at 68-70mph.

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5.3 with 6L80. Right now if I am crushing at 80 and hit even a small hill it has to unlock the converter . That's without a load just the driver . At 80 I'm right at 1700 rpm now . I drove a truck like mine with 3.42 and it was night and day difference . 

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Here's some numbers for reference assuming you have ~32in tall tires like most trucks do.


3.42's at 80mph is ~1,930rpm

3.73's at 80mph is ~2,100rpm

4.10's at 80mph is ~2,300rpm


Drop about 250rpm off of those if you went 70mph. They say never fear the gear but if you are using stock size tires I would say the 3.73's are best suited with that 6L80e transmission.


I've towed an open car trailer that was about 6,000lbs combined with 3.42's and it had zero trouble. Having 3.73's would have just made it easier.

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3 hours ago, Mike72 said:

Thank you . I'm going to put 33's on it when I replace my tires. Now I just have to find a place to change the gears for me for a reasonable price 

34s (275-65-20) and a 3.73 gear will be almost the same rpms as 3.42s with the stock tire size.  Pulling 7K pounds, you'll want to tow in 4th.  What kind of truck Mike?

Edited by swathdiver
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On 3/27/2020 at 8:32 AM, Mike72 said:

2012 crew cab short bed 


RWD or 4WD?


You're maxed out or over towing capacity with 3.08s.  Do you have K5L?  I see that installing those 3.73s would give you GCWR of 16,000 pounds and trailer weight of 10,400 on the bumper if 4x4.  Big difference in pulling power.  Of course, that's not official.

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