Flame Suit On: Lower a 4x4 (for MPG purposes)

RideZX6R · Jun 26, 2017

Just curious if anyone has lowered a 4x4 twin?
I sold my V6 Colorado about a year ago, and bought a new Camaro 1LE. I wanted to keep the Colorado at the time, but couldn't afford both.

Now I can afford both, and would like to purchase a Duramax 4x4...

Why lower a duramax 4x4?

Well it'll never go offroad, but we do get snow occasionally in the PNW and I'd like to be able to get thru it, hence 4x4, but no need for the height it provides
The truck will occasionally tow the Camaro so the duramax
Otherwise the truck would be used for commuting and again hence the duramax
Lowering it should help with MPG
It will look undeniably cool with a drop and a set of nice wheels, and perhaps get a little better MPG doing it.

So - Has anyone done it? Things to watch for?

onebaddz · Jun 26, 2017

I don't think my mileage got any better with the drop. I thought it might when I did it, but I don't know that we are getting the air dam close enough to the ground to make a significant change in airflow under the truck.

I don't know if anyone has tried it with a 4x4 yet. It's been discussed, it wouldn't surprise me if one popped up in here.

You can normally lower a 4x4, but not as much as you can lower a 2x4 simply because of the front shafts. The kit for our truck isn't adjustable in the rear, so you'd have to do some customization to the shackles to keep from lowering all the way. To lower it less, they'd need to be longer between the bolt holes. I'd redrill it farther out, weld up the old holes, and roll on. Unless it needs to be significantly longer for the height you want, then you'd just section it and add metal to make it longer if you're a good welder, it'll be an important weld for sure.

Normally with the big trucks lowering a 4wd is limited to about 2" in the front, just watch your shafts so they don't bottom out and just decide how low to go on the fly. Then adjust the rear to match.

Mine is a Dmax Z71 but a 2wd.

lqdchkn · Jun 26, 2017

Should be possible. Don't think anyone has done it though.

bac522 · Jun 26, 2017

I doubt you'll see much of a difference in MPG...you're still pushing the same air mass out of the way.

onebaddz · Jun 26, 2017

bac522 said:
I doubt you'll see much of a difference in MPG...you're still pushing the same air mass out of the way.

He's also got a Camaro, and in the Camaro world it's known that lowering them does increase MPG. My wife's Camaro gained MPG. It's about cutting airflow under the vehicle as well as air directly into the tires. We already have a big air dam to help out, and that's what the small flaps in front of the rear tires are for as well. I was hoping to see some difference on this truck as well, but unfortunately that hope wasn't realized. Either the air dam and flaps are already doing all we can do, or we need to get even closer to the ground to stop enough airflow to help even more.

lqdchkn · Jun 26, 2017

onebaddz said:
He's also got a Camaro, and in the Camaro world it's known that lowering them does increase MPG. My wife's Camaro gained MPG. It's about cutting airflow under the vehicle as well as air directly into the tires. We already have a big air dam to help out, and that's what the small flaps in front of the rear tires are for as well. I was hoping to see some difference on this truck as well, but unfortunately that hope wasn't realized. Either the air dam and flaps are already doing all we can do, or we need to get even closer to the ground to stop enough airflow to help even more.

Your front air dam is already hella low. I don't think getting any closer could help

CCEnthusiasts · Jun 26, 2017

The cost of the lowering kit would negate the mpg increase savings (if there even is any). The only thing that can be done to increase MPG and actually save money, is keeping your truck stock.

onebaddz · Jun 26, 2017

For the record, I'm on the ultimate MPG hunt. I'm lowered and tuned so far. I plan to add a bed cover before the end of the year. I have the stuff in hand to convert to the electric fan from the V6 truck since the Diesel comes with an electro-viscous fan and that's my next mod. They may be all tiny changes in MPG and possibly even wives tales, but I'm going to find out if we can get either 30mpg in town or 40mpg on the highway at 75mph.

I haven't done the fan yet because EFIlive doesn't have the fan tables. I'll have to undo my EFI Live DSP4 tune, get the fan working right with HPTuners, then re-read the tune with EFIlive and do a DSP4 tune conversion again. It'll be a big weekend of flashing and modifying tunes.

I can be told all day long that it'll never pay itself off, but if I listened to those arguments I wouldn't own a diesel to begin with. I enjoy doing these things

RideZX6R · Jun 27, 2017

For the record, I was referring to better MPG on 2 counts...

1 lowering it
2 bigger wheels making the gearing a bit longer (nothing too wild, just incremental).

I'd still like to lower it, simply because it'd look nice. I don't think I'd end up with 20s on it. But a set of 18s or maybe 19s with all seasons would probably do the trick.

Thanks for the input guys. Guess I'll have to consider getting the kit and perhaps modding it to fit.

White016 · Jun 27, 2017

RideZX6R said:
For the record, I was referring to better MPG on 2 counts...

1 lowering it
2 bigger wheels making the gearing a bit longer (nothing too wild, just incremental).

I'd still like to lower it, simply because it'd look nice. I don't think I'd end up with 20s on it. But a set of 18s or maybe 19s with all seasons would probably do the trick.

Thanks for the input guys. Guess I'll have to consider getting the kit and perhaps modding it to fit.

Just remember its not wheel size that would make it geared higher, its tire size. So you would have to go with a bigger tire and I wonder if that would hurt MPG? Anyway, how would you lower it in the front? On a 4x4 you cant find lowering parts right? so cut the springs I guess???

bac522 · Jun 27, 2017

onebaddz said:
I was hoping to see some difference on this truck as well, but unfortunately that hope wasn't realized. Either the air dam and flaps are already doing all we can do, or we need to get even closer to the ground to stop enough airflow to help even more.

Exactly...I own a Corvette and use to race it so have a good idea on aerodynamics...Camaro's and Vettes are designed to flow through the air better then our trucks...I still say one will see negligible difference in MPG by lowering our trucks, front end is just too big.

Duken4evr · Jun 27, 2017

A good potential reason to lower it given your intended use isn't so much for gas mileage but better handling.

Years ago I had a 4x4 Ford Ranger, it had big lift blocks in the rear end and sat very ass high as a result. The front ends on those old Rangers were pretty marginal to begin with, and the high tail exacerbated the situation - the truck rode like crap. Pulled the lift blocks out and put in small spacers which had the truck sitting perfectly level, it rode much better afterwards. I put in some helper springs to keep it from sagging too much under load and it all worked out quite nicely. Would love to be able to do this to my new Canyon, but it sits ass high with the springs sitting right on the rear axle. I really don't want to lift the front end to level it. The truck is sometimes a bit jittery when empty and rides a lot better with a dirt bike in the bed, that is for sure...

onebaddz · Jun 27, 2017

RideZX6R said:
For the record, I was referring to better MPG on 2 counts...

1 lowering it
2 bigger wheels making the gearing a bit longer (nothing too wild, just incremental).

I'd still like to lower it, simply because it'd look nice. I don't think I'd end up with 20s on it. But a set of 18s or maybe 19s with all seasons would probably do the trick.

Thanks for the input guys. Guess I'll have to consider getting the kit and perhaps modding it to fit.

Oh I support lowering it no matter what >

I've been hoping for someone to produce 3.23s or 3.08s since I bought it, but it's a unique rear end and there's nothing out there right now.

Suns_PSD · Jun 27, 2017

I like the lowered trucks and for most people, it's more practical.

I'm surprised that onebadzz didn't see any increase in mpg.

Onebadzz, buy 18" (or 17!) forged wheels that are narrowish and have a flat profile and some hard lightweight tires pumped up to about 50psi. There is notable mpg gains in that mod.

mhr900ss · Jun 27, 2017

my 2c: the front wheel wells are really tight; lifting/lowering with stock wheel sizes will not be a problem but my 305/55 tires required cutting the lower front plastic about an inch and the bottom of the rear well is really tight when turning. Lifting usually gives room for a marginally bigger tire but lowering may not allow a bigger tire to fit.

onebaddz · Jun 27, 2017

Suns_PSD said:
I like the lowered trucks and for most people, it's more practical.

I'm surprised that onebadzz didn't see any increase in mpg.

Onebadzz, buy 18" (or 17!) forged wheels that are narrowish and have a flat profile and some hard lightweight tires pumped up to about 50psi. There is notable mpg gains in that mod.

In the interest of full disclosure I should say that my heavier than stock wheels could have eaten up any negligible gains from lowering. I lowered and swapped to heavier 20s at the same time. They aren't any wider than stock, but they are definitely heavier. If someone were to keep stock wheels and lower it might be a better indicator than mine.

I want different wheels, I was pigeon holed into these with lack of availability when I bought them. There still aren't any wheels I really like for these trucks, most everything available is more offroad style. I talked to our rep at CCW and he said they had perfect blanks to build SP600s for our trucks. I can't bring myself to go more narrow nor smaller wheels even though I'm on an MPG hunt.

White016 · Jun 27, 2017

onebaddz said:
In the interest of full disclosure I should say that my heavier than stock wheels could have eaten up any negligible gains from lowering. I lowered and swapped to heavier 20s at the same time. They aren't any wider than stock, but they are definitely heavier. If someone were to keep stock wheels and lower it might be a better indicator than mine.

I want different wheels, I was pigeon holed into these with lack of availability when I bought them. There still aren't any wheels I really like for these trucks, most everything available is more offroad style. I talked to our rep at CCW and he said they had perfect blanks to build SP600s for our trucks. I can't bring myself to go more narrow nor smaller wheels even though I'm on an MPG hunt.

on the highway a heavier wheel won't matter right? I think those wheels look great! Cool looking truck.

onebaddz · Jun 27, 2017

JScottM said:
on the highway a heavier wheel won't matter right? I think those wheels look great! Cool looking truck.

It's a bigger deal with stop and go, but it'd have to affect highway mileage too on some level. Not to mention they sit out almost an inch further than stock, increasing drag. Now that I think about it I wish I still had stockers to bolt on and try for a while just to know.

Thanks, I do love my truck.

Flame Suit On: Lower a 4x4 (for MPG purposes)

RideZX6R

onebaddz

lqdchkn

bac522

onebaddz

lqdchkn

CCEnthusiasts

onebaddz

RideZX6R

White016

bac522

Duken4evr

onebaddz

Suns_PSD

mhr900ss

onebaddz

White016

onebaddz

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