Gear swap 4:10 to 4:56

cmysstailights · October 31, 2019

I have a 15 6.0, i tow a cargo trailer daily 6klbs and my tt 10klbs 6 times a year. Looking for more out of the truck. Havent been able to find a diesel in my price range (have 3.5 yrs left to pay off, so wanna keep the same payment time frame.) Has anyone did a gear swap and how does it tow and how much of Difference in mpg. The tt gets towed in the mountains and theres some nice inclines.

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SierraHD17 · November 1, 2019

Went from 3.73 to 4.56 in my 17 with a 295/60/20 I had installed prior to the gear change. For rpm just use a calculator for your own combo. Your 6th gear is 0.67:1. For reference sake I still turn roughly 300 rpm less than my 4.10 geared stock 245/75/R16 equipped 4L80e trucks do at the same ground speed.

If I did it again... and I may due to paying for screw ups to work on my truck and now the rear howls I would go 4.88 with my tire. There really isn't too much gear for these heaps and it just gets them in the RPM range they make power in faster. I can pull hills better than any 6 speed 4.10 gear truck I have had can and I just manually shift it to keep the rpm where I want it.

I don't track mileage... don't care lol. I put gas in the truck when the gauge gets low. If you want to know mileage drive the truck on the highway and do not let it shift into 6th.. the rpm will be similar to what 6th gear becomes after the gear change.

Edited November 1, 2019 by SierraHD17

i82much · November 2, 2019

i cannot see spending that kind of money unless you are doing the lift and bigger tires thing. i think it will help some but you aren’t going to go screaming up a steep hill with your travel trailer just by regearing.

SierraHD17 · November 2, 2019

You actually have to do it to be able to understand. it's quite noticeable and well worth the effort as every little bit helps. The idea is it helps you not go "screaming up hills" as you don't have to downshift into second for every incline.

And yes this is coming from someone that actually re-gears their stuff and doesn't just theorize on the internet. This isn't my first re-gear either... my 05 1500hd was 3.73 and I went to 4.10 with it.. Blazer was 3.08 and went 4.56... Caprice was 3.08 and went to 3.42 etc etc.

Even GM has figured the mechanical advantage part out on their own hence why a 3.73 truck is rated to pulled over 3000 lbs less than one equipped with 4.10's.

If I were the OP I would do 4.88. As I previously stated since my rear gear set now howls after bozo repairs I might just buy some 4.88's and do it myself this time as I never drive the truck anyway so time is not of the essence.

For fun in my particular application my rpm would increase by 150 to 2300 at 70 mph with 4.88 as opposed to 2150 now with 4.56. And yeah.... that's still 300 rpm less at 70 mph than my old LQ4 4l80e 4.10 geared truck turns with it's factory 245/75/16's. Even at a 5.13 gear I would still be 200 rpm less rpm than that truck at 70 mph.

Edited November 2, 2019 by SierraHD17

2017HD · November 3, 2019

My 07 6.0L with the 6speed and 4.10 rear gears towed my 6000lb TT with ease. That motor loves to rev to 3000-4000 in order to get max torque. In 4th gear this rev range resulted in a speed of 55-60 - I felt nothing wrong with that. The only way I would do this kind of change is if I went to larger wheels and tires that effectively reduce the rear end ratio.

cmysstailights · November 3, 2019

Heres a pic of my setup. My route usually consists of 7% grade twice. Rt 17w in ny, wurtsboro mountain . 1 stretch is about a mile and a half the other is around 2 miles. Looking for a diesel, but not having any luck with in my interests.

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SierraHD17 · November 3, 2019

Then just hold out for your Duramax... you won't be happy with this no matter what as it's not what you want anyway.

cmysstailights · November 3, 2019

Then just hold out for your Duramax... you won't be happy with this no matter what as it's not what you want anyway.

True, just sux. I keep upgrading trucks cause my lifestyle change lol. Now looking for a 3500 high country diesel. And keep same payments and time frame left lol

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cperk · November 4, 2019

Heres a pic of my setup. My route usually consists of 7% grade twice. Rt 17w in ny, wurtsboro mountain . 1 stretch is about a mile and a half the other is around 2 miles. Looking for a diesel, but not having any luck with in my interests.

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What kind of front bike rack do you have? What did you have to put on for mounting, a front hitch?

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i82much · November 4, 2019

i have done a few gear swaps myself. i went from a 3.23 to a 3.90 axle in a four speed 65 GTO ... that put a smile on my face!!!!

but here, sinking that kind of money into two axles on a nearly-new truck doesn’t make sense to me. yeah, maybe you will be happy, or maybe you will be out a bunch of cash and still want a diesel. the problem is that you have to spend the money to find out.

if you want a real reason to regear, beat that sumbitch until you break a rear, like i did doing 6k clutch drops with my 3.23’s ... that’s how i wound up with 3.90’s!!!

cmysstailights · November 4, 2019

What kind of front bike rack do you have? What did you have to put on for mounting, a front hitch?

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Got it off of etrailer.com. simple bolt in, just loosen recovery hook bolt

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cmysstailights · November 4, 2019

i have done a few gear swaps myself. i went from a 3.23 to a 3.90 axle in a four speed 65 GTO ... that put a smile on my face!!!!

but here, sinking that kind of money into two axles on a nearly-new truck doesn’t make sense to me. yeah, maybe you will be happy, or maybe you will be out a bunch of cash and still want a diesel. the problem is that you have to spend the money to find out.

if you want a real reason to regear, beat that sumbitch until you break a rear, like i did doing 6k clutch drops with my 3.23’s ... that’s how i wound up with 3.90’s!!!

Had a 2000 ss used to dump the clutch at 5k with et streets on stock rear. She took a beating and never failed. Eventually went to 4:11 but sold her right after that.

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