# Gear Ratio Question



## wfishtx (Apr 10, 2006)

Will be going on Thursday to buy a new GMC and can't decide on which rear axle gear ratio I should go with, the standard 3.23 or the upgraded 3.73.

Is there a big difference in performance between the two and is going with the 3.73 really worth it? Also, what kind of gas mileage difference would I be looking at between the two? I assume the 3.73 won't get as good a mileage as the 3.23, but is it enough difference to really matter?

Thanks


----------



## Supergas (Nov 30, 2004)

*3.73 for towing.....*

If you are going to tow anything of substance, get the 3.73 gears. The 5.3 that is standard in these trucks has a torque range that doesn't start until around 3700-3800 so you will need the higher numerical gears...

I had an 04 with the 3.73 & the 5.3 & it was OK except it hunts a gear if you go over 65 or under 72 even in the Tow Mode.

My new 07 GMC VortecMax 6.0 w/ 3.73 gears tows my 21' Wellcraft at 70 without hunting gears.. This is due to a different tranny than in the standard trucks & probably a different program for towing with the Max Towing Package..

Good Luck...

Supergas


----------



## wfishtx (Apr 10, 2006)

Curious what you mean by it "hunts" a gear if you go over 65 and under 72?

As for the towing, there will be little to no towing for the next several years at which time I will be getting on a deer lease and doing a lot of hauling of a couple of four wheelers and deer blinds and feeders. Outside of that, the towing will be limited.


----------



## thundertrout (Jun 22, 2006)

hunting a gear is when your trans goes just say ur in od it will shift down a gear.
correct me anyone if i'm wrong.


----------



## Guest (Dec 26, 2007)

Just my opinion, but the 3.73 is the perfect all around gear. A 3.23 is just too high for a pickup. Hauling and towing with that gear puts big strain on your running gear, as for milage, probably 2-4 mpg difference. The upgrade you spoke of may come with a limited slip differential also a plus.


----------



## sqwaby (Aug 4, 2005)

Gm also offers a 3.42 ratio I believe. Might want to check that out. I run a 350 with a 3.73 gear, I pull a 16 alum. boat, but have towed up to about 4-5K lbs no sweat.


----------



## wfishtx (Apr 10, 2006)

Let me make a small correction to my original post...the two gear ratio options are a 3.43 or a 3.73. Sorry about that.

As of right now I'm probably leaning towards the 3.43 for better fuel efficiency since I have nothing specific to haul right now. I don't own a trailer or a boat that would require the 3.73.

My biggest concern is driving up and down hills with the cruise set. I don't want the truck down shifting all the time going up hills. I want it to have enough torque/power to get up a hill without having to downshift, which I feel confident the 3.43 will do. Anyone not agree, or does anyone currently have the 3.43 that can testify to its performance driving through the hill country?


----------



## thundertrout (Jun 22, 2006)

my z71 has the 373 gears it will pull anything i want with it,i prolly get 17 18 mi the hwy driving 70.gas milage gets better when the motor starts to break in.


----------



## wfishtx (Apr 10, 2006)

Yeah, every 4WD I've looked at comes with the 3.73 rear end. I think its standard on those trucks.

I just spoke with my dad and discovered his has a 3.23 rear end, which he is more than pleased with and I've seen him pull more than I would ever need to pull, so I'm probably going to go ahead and go with the 3.43, which provides even more hauling capability than his does.

Thanks for all the help.



thundertrout said:


> my z71 has the 373 gears it will pull anything i want with it,i prolly get 17 18 mi the hwy driving 70.gas milage gets better when the motor starts to break in.


----------



## Roby (Jul 12, 2005)

I ran a 3.42 in a 94 C-1500 with a 5.7 for 10 yrs. At times I could have used a little more gear but for 95 % of my towing it was fine. For 99 % of use it was fine. Be sure to get the locking rear end. I believe it is more important than the difference between a 3.42 and a 3.73.


----------



## chazmac (Aug 10, 2007)

I have a 05 chevy ext. cab 2wd with the 373 gears and I would not have anything else. MPG on average is 17 and that is driving from spring to katy every day. On the highway about 19. I have pulled light trailers and heavy trailers and it just works. As far as shifting alot I never pull in O.D. you are asking for transmission problems even with the towing package that comes with the aux. transmission cooler. I would suggest the 3.73's. It will not hurt mpg enough to notice and when you do hook up to something you don't have to worry about it.


----------



## jeff.w (Jan 22, 2006)

For a lot of running around town, short trips, occasional towing, definitely go with the 3.73's. If you plan on doing more highway driving, (longer trips etc), go with the 3.42's. 

I've got 3.73's in my GMC Sierra, and have absolutely no regrets.


----------



## thundertrout (Jun 22, 2006)

ditto on the locking rear end it makes for quick turn arounds on those narrow roads.


----------



## Harley (Jul 5, 2007)

Yep, posi rear is the way to go if you can. 3.42 gears are a great all around ratio. I pulled a 6000 boat with those gears and had no problem. Gas mileage is better too than the 3.73's. 
I just bought a new Tundra with the 5.7 engine. I have been a GM guy all my life but this Tundra is something else. It is way quicker and will pull way more than any 1/2 ton I have ever owned. About the same MPG as the Chevy 5.3 too.
Good luck.


----------

