5.3 3.42 gears vs 3.73

mookdoc6 · September 15, 2016

4wd isn't even in question and doesn't have anything to do with the towing except I do go up one steep gravel road in the summer towing my travel trailer that I would not be able to make it up without the 4wd. I also use it in the snow and ice in the mountains in the winter. As far as I am concerned if it is not 4wd it is not a truck.

Mike

OK get your 4wd! 20% of GMC 4x4 SLT go get you one! You will love it.....8speed too! Hurry up! we want to see pictures..............

spenpet · September 16, 2016

i dont think i'm adding anything other than to reiterate what most everyone else is saying about the tranny. if you can upgrade to the 8sp, i would 100% recommend that...they created that more so for towing than they did for MPGs.

i had an '08 5.3 3.42 and didnt haul much, but occasionally...motor had plenty of power, but it did like to drop down quite a bit even on gradual inclines. the 8 speed with the 3.42 should give you the best of both worlds pretty good MPGs (when not towing) and plenty of gear to get your trailer moving.

i got my truck about 21% off of MSRP, so it helped me be able to afford the upper trim...if you can wait...October is the best month to buy a truck...its just around the corner...

SamSin · December 29, 2019

My 2015 Z71 GMC Sierra is rated for 9,200 with the 3:42 axle and tow package. I'm currently towing a 34" 7000# TT with a WDH. Probably another 12/1500 extra lbs. when loaded. Normal speed when towing is about 60 to 65 MPH, and average around 11 to 12 Mpg when towing. My best has been 13.1mpg. I went to a local spring shop and had an extra leaf installed, plus I added a Road Active Suspension (RAS) kit. I didn't get the spring addition to allow for more weight, but to enhance the suspension I already had. It would sag even though everything was within specs, and I didn't like how it handled on the curves when towing. It now tows like a dream with little to no sag. With the added spring the difference in the ride is almost negligible. So for me it is a good all around truck, the 3:73 would give me less MPG, and I doubt would have towed any better than my current set up . . . Without the trailer I have averaged over 22 MPG.

From what I gathered from the spring shop, was that most trucks today have a softer suspension because most people want a car like ride, so there may be some rear end sag even though they are rated for a specific weight, trucks aren't capable of their full potential due to the softer set up. The added spring will not change the trucks loaded carrying capacity, but will help supplement the existing set up. I know in my case, it eliminated the sag and with the WDH, there is no dip at all. I went with the spring shop, instead of an aftermarket add on leaf, with their expertise they were able to add the extra leaf without changing the ride characteristics very much. it rides just as smooth (perhaps a little stiffer, but then again I like a truck to ride like a truck) and has eliminated any lean on the curves when towing.

If you aren't sure of your tow ratings, their are a few sites where you can type in your VIN# and it will give you the specs on your tow vehicle. My VIN lookup stated 10,900, but in the real world it is 9,200 lb. rated.

The truck does not strain, although the engine does search for gears on occasion, depending on the incline, but that is when the tow haul mode kicks in. When I know an incline is coming up, I will speed up before reaching the base of the hill. I also bypass the AFM, and use M5 mode when towing. The 5.3L is a workhorse . . . Funny thing is I had a previous 25' trailer rated slightly over 6000 lbs. and the difference in MPG didn't change with the heavier trailer. It is slower off the line, but then again I'm not looking to win any races towing a trailer.

The Z71 package just happened to come with the truck when I purchased it, from my understanding The Z71 package offers specially tuned springs and mono-tube shocks for the suspension to better support the vehicle's weight and tire contact, as well as further dampen shock, combined with an automatic locking rear differential to improve the distribution of drive shaft power. Whether it makes a difference in the towing, I haven't a clue.

I have been towing for several years now, and am very comfortable with what I have at present. I also like the fact that after I set up at the campsite, I have a vehicle that is fairly decent on gas to go sightseeing the area. 22MPG using regular vs. maybe 16MPG using premium gas comes out to a nice dinner every now and then.

I'm sure others will have their opinion, but just thought I would throw my two cents into the mix. You need to feel comfortable and safe with your tow vehicle regardless of what it is. If you're driving with white knuckles while towing, you need a different truck, a different trailer, or some modifications by professionals.

Anywho . . . that's my story and I'm sticking to it.