Anyone upgrade their axle ratios to 3.73's?

[Sparkyz07Denali]

i was curious if anyone has upgraded their axle ratios to 3.73's? I have a 07 Denali, im wanting some more grunt off the line. was curious if anyone else has done this. and what the highway manners were?

 

[B-train]

I'm curious as well, have an 08 myself.

What are your plans? Break everything apart and install new gear sets? Or have you found a donor vehicle with the correct ratio?

 

[Doubeleive]

I have had a silverado with 3.73 it is a little snappy off the line, your 07 should have 3.42 already so changing to 3.73 might not be a huge difference
basically the math on it is you gain a little low end (and some towing capability) and loose some slight higher end, that's the trade off

 

[swathdiver]

i was curious if anyone has upgraded their axle ratios to 3.73's? I have a 07 Denali, im wanting some more grunt off the line. was curious if anyone else has done this. and what the highway manners were?

You will raise your cruise rpms at 70 mph from about 1750 rpms to 1909 rpms mathematically. Yes, she will have more giddy-up and towing prowess.

I have a 2012 Sierra with factory 3.73s and am going to put 3.73s in my Yukon soon. The engine doesn't seem to mind the extra rpms at speed at all.

 

[B-train]

I concur. These motors are super happy right around the 2k mark when cruising. Ice found some of my best fuel economy between 1850 and 2100 rpm.

Keep us posted on what you intend to use. I think it would be a nice upgrade as well. I've also toyed with 4.10s too.

My dad had a 2000 silverado 5.3 with 4.10 factory. That thing would fly and pull up grades with ease. Still got 18-20 mpg highway too. Those were good trucks......to bad they rotted out so quickly and were cast aside. Major bummer

 

[Sparkyz07Denali]

I have tossed around the idea of 4.10’s but have concerns about highway rpm’s at 70-75

The plan would be to put all new gears and bearing in the axles. Won’t be any different than doing it on a 4x4 I have done a lot.

 

[swathdiver]

I have tossed around the idea of 4.10’s but have concerns about highway rpm’s at 70-75

The plan would be to put all new gears and bearing in the axles. Won’t be any different than doing it on a 4x4 I have done a lot.

4.10s on stock size tires and the 6L80 would turn 2,098 rpms @ 70 mph and 2,248 rpms at 75 mph. Some of GMs 2500 and 3500 gassers run 4.10s with the 6L90 so they were made for it.

I considered it, saw a lowered and modified Sierra just leap off the line but both Sierras spin the tires off the line on the street already. One of them has stock size KO2s and 3.42 gears and the other the 3.73s on 35" tires. That and the higher rpms are why I'm going to stick with the 3.73s.

@B-train Consider the difference between your Dad's Silverado and a 2009+ Silverado equipped as shown.



Now here are the effective ratios for each gear with the ones Sparky is considering:



Now also consider this, there's a young man sweet on one of my daughters who comes around with a Ram 1500. He's been victorious in several 0-60 runs at the street drags. The 3.73 geared Sierra on 35s gets him off the line but he quickly runs her down. The motor's in each are similar power wise so I endeavored to find out why and here is what I discovered:




Look at that first gear ratio! In order to compete with that gear wise we'd have to go with 4.56 gears. We installed the BlackBear tune that Justin sent over yesterday and when my daughter got back from an impromptu drive she was all smiles and said it went "zoom, zoom" like never before! Fun stuff!

 

[B-train]

That is a lot of good info! Thanks for taking the time to put that together. Much appreciated!

 

[intheburbs]

I can make a direct comparison, given the two vehicles in my sig.

The Suburban is 1000 lbs heavier and has 50 fewer HP, but also has a tune.

The Denali jumps out to a quick lead, but then is unable to walk away. The Suburban stays about two car lengths back right up to 100, then, of course, overtakes and walks away.

But personally, given the cost of regearing (not something I can do myself), I wouldn't do it unless it was at least a double jump. Cost/benefit doesn't make sense. 3.42 to 3.73 just isn't worth it. 3.42 to 4.10, yeah, that might be worth it.

Of course, given my Denali already gets frightening mileage with the 3.42s (and needs premium), the mileage running 4.10s would be downright terrifying.

 

[Sparkyz07Denali]

Oh I may go to 4.10’s then. And you don’t buy a Denali because you wanna conserve gas. At least I didn’t.

I used to have a ‘13 SS Camaro, bought it new. 2yrs later was stolen. Life has happened. And I’m in a spot where I need to haul 4 English mastiffs. So I have a Denali. And I can build it with the similar of not the same mods I did to the Camaro (which had 515rwhp)

This is amazing info. Thank you. Still leaning toward 3.74’s since I drive almost an hour one way to work.
Then again. It’s a 4 day work week. (I work 12’s) so it could still work with 4.10’s