I have an 04 GMC Sierra 1500 crew cab with the 5.3L engine and 3.42 gears. The previous owner added 20" wheels and tires and a flowmaster muffler, otherwise the truck is stock. My Outback 30BHQ is around 7500lb dry, and I want to add some mods to improve towing. I also only get 12 mpg city and 14 hwy not towing and I am a fairly conservative driver. I have had the truck checked out by the best mechanics in the area and they say it there are no issues with it. I wonder if the taller tires might have something to do with the mileage. I currently am running 1500 rpm at 60 mph (Corrected). My thoughts are to change to a 4.10 axle ratio and purchase a programmer. By my calculations, the 20% lower gear ratio should increase my rpms at 60 to about 1800. Any experience/recommendations on a programmer? Will these changes help my towing ability?

Changing to 4.10 gears will definitely help. However, you don't have enough truck for a 7500# Dry Weight trailer so your towing experience is still going to suck. That generation of 1/2 ton chevy's is practically limited to around 6,000# loaded TT towing weight (note I said loaded not dry meaning probably 4,500# dry). (I have a 1/2 ton '05 with your engine and heavy duty tow package, and absolutely would not tow your empty trailer with it, much less loaded. I love that 1/2 ton but it is just not enough for your trailer)

Will these changes help my towing ability? No. You could even add a supercharger but that will only increase power, not towing ability. There is much more than just power required for good towing ability. You'll be lacking in payload, axles, suspension etc, as with most 1/2 ton trucks trying to tow that size and weight of TT. You're probably looking at close to 9000lbs once loaded up so even if you could pull it you're likely over several of the trucks ratings.

New member, welcome to the Forum.I'm blunt...often probably too blunt:You have a big trailer and a relatively (light duty)truck. Pouring money into mods like re-gearing and a programmer is not going to give you better mileage or more payload. You will be wasting your money and will probably soon need transmission work.It is a 1/2 ton truck and a heavy bunk house trailer...probably means family - kids and lots of gear.You are in 3/4 ton territory...big block or diesel.Hopefully others will give you a more positive outlook.

I hada 2002 Chev with 5.3, 3.73 and towed 7000-lb (loaded) 5vr. Wasn't a lot of fun, especially at high elevations or into headwinds.Replaced 5with with a 9300-lb (loaded) 5vr and replaced truck with 2500 Chev, 8.1, 4.10. Towing was fun after that. Acceleration, no problem merging on interstate highway. Having the 4.10, I towed at 58-59 mph, just after o/d kicked in. Mpg's towing, avg 9.3 - about the same or slightly less than the 1500.You're in 2500 territory, which screw around putting band-aids on your 1500?

X2 on what was posted above. Mine is an 04 also with 3.73s and is rated to tow around 7700lbs if I remember correctly. If your truck is a 2wd it may be a little more. Besides the tow rating your payload isn't that great, I'm at 1000 lbs with me in the seat and 3/4 tank of fuel.I am right at 7000 lbs, my GVWR, with this set up, ready to camp. Thats just me and my two little dogs and my stuff.I can get around 17 mpg on the road solo if I keep it under 65 mph. 75 mph gets me 15 mpg. Towing like the pic under 65 mph is 12-13 mpg. I'm running 285/65-18 tires.

Power mods on Sierra 1500 CC with 5.3L | Good Sam Community

16 Replies

camp-n-family
Explorer
Mar 28, 2014
The 20's are what's killing you.

Only true if the overall diameter was increased as well. A lot of trucks offer 18 or 20" rims but have the same tow rating and gearing because there is no difference in the overall diameter. The 20s will be lower profile than the 18s to keep them the same.
mkirsch
Nomad II
Mar 28, 2014
The 20's are what's killing you.

If going to 4.10's only gets you UP to 1800RPM at 60MPH, then your tires are way way too big around.

My 3.42-geared truck turns 1900RPMs at 65MPH on stock 16" tires.

It will also improve your gas mileage by about 20% because you won't be downshifting at every puff of breeze or every slight uphill.
dodge_guy
Explorer II
Mar 28, 2014
Yep, time for a HD 1/2 ton or a 3/4 ton truck. My trailet is 7100lbs dry and i'm towing it with a V-10 Excursion with 4.30 gears. My trailer is approx. 9200 lbs ready to travel, your trailer will weigh in around the same ready to travel depending on how much stuff you pack.

Get a bigger truck!
MitchF150
Explorer III
Mar 28, 2014
I'd say just sell the beast to a 20 something kid... They will love the 20" wheels and the 'slowmaster' muffler! :)

Take that money and the money you want to spend and use that for a down on a truck that will handle a #7500 dry weight trailer...

I wouldn't want to tow that with my new F150, as I'm sure it'll have more TW than I'd care to deal with...

Just my opinion on the deal...

Good luck!

Mitch
goducks10
Explorer
Mar 28, 2014
Most of the tuner mods for gassers don't improve HP until you're way up in the rpms. Normal towing rpms will be too low to see any benefits.
APT
Explorer
Mar 28, 2014
Take your mod budget of say $1500-3000. Buy some OEM 16" wheels/tires, take offs used. Sell the 20" wheel/tire combo. Sell the truck. A similar vintage/condition 3/4 ton GM 6.0L will have far more power, better gearing (3.73 or maybe 4.10 stock) and far more payload to handle 9000 pound loaded TT. Oh, the 6.0L seems to get the same FE as your truck. Mine with 6-spd does even better.

Seriously, any modification money you "invest" in the current truck will be worthless at time of sale, just like those 20" wheels mounted on the truck. Get the right tool. If you can afford a 2007.5+ GM HD with the 6-spd, you'll poop your pants with the performance improvement. I had a 2003 F150 5.4L/3.73. Today's trucks are just better.
ib516
Explorer II
Mar 28, 2014
The re-gearing might be worth it, but skip the power programmer. They add very little power and usually to get a 5 or 10 hp boost they require you to burn premium fuel.

Personally, my opinion is "you got what you got". If it doesn't do the job, you're better off buying one that can.
goducks10
Explorer
Mar 28, 2014
I'd get the Dmax power-up kit:)
Trackrig
Explorer II
Mar 28, 2014
My two cents is what the OP wants to do WILL give him more power, but NOT more towing capacity. There's a difference that shouldn't be confused.

Bill
TurnThePage
Explorer
Mar 28, 2014
A bigger truck would be the ideal solution, but... Regearing will cure a lot of what ails your current truck, and most likely prolong the life of the tranny, vs hurting it. You'll probably even see better mileage in the city. LT tires would be a VERY good idea too.

My old, tired truck woke up and took notice when I went from 3.55 to 4.10. That was over 10 years ago, and it's still going strong. My trailer is quite a bit lighter, but I also used to squeeze two smaller ATVs, a generator, and various other stuff into the bed too. Food for thought.

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Power mods on Sierra 1500 CC with 5.3L

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