Will 5.3 to 6.0 (LQ4) make a big difference in towing?

[Mudsport96]

Im in the gear ratio advantage camp. Yeah a 6.0 makes more power everywhere but at what point do you stop adding.
The trans is the next weak link, so now you have to repace it when it breaks. Do you go back to a 60e? A 65e? Find a 70e? Yes you can use a 70 in a 60 application with minimal effort to swap from what ive read.
Or take the big jump to an 80e? Wiring, tune, driveshafts.
Find out what gears put you at a good towing rpm and get those.
Personally, if its mainly for towing the boat, i would go straight to 4.56s. More mechanical advantage everywhere. And has the added bonus of taking some load off of the transmission because of the ratio increase, making it easier to move the load.

 

[George B]

I am also in the lower gears camp.

 

[THarber]

wrong post

 

[Teamwieland]

I tow with an LQ4 in my 2006 Denali xl and I also live in the mountains. Town sits at about 7,000 feet in elevation. While my towing has not gone over about 4500lbs, my LQ4 and my rebuilt 4L65E trans handle the boat I haul up and down the mountain roads for a close family friend, pretty easily. I’m not necessarily winning any speed races going up the grades when I’m towing but it pulls and pulls and pulls faithfully and doesn’t struggle. All I’ve done under the hood is a spectre intake, and a mild magnaflow muffler in pace of the factory muffler, and had blackbear performance do a tune. That’s a piece of the puzzle I would absolutely recommend. He tweaked a lot and adjusted for being at altitude most of the time. Here’s what I tow most often behind my Denali.

I’m at about 7000 lbs, plus the Suburban is usually loaded with 7 adults and all the stuff that goes along with it.

 

[Teamwieland]

What kind of altitude are we talking about? I appreciate the feedback from @adventurenali92 , but to be honest, the mountains in Ca. altitude are a whole different ballgame. We start out at 5280, and go up from there (5,861 here in my town). Once you head to the mountains, we’re usually at 10k+ pretty quickly. So I think that’s a pretty important piece to the puzzle.

From a quick glance, I’d say gears are the cheapest, most effective option to make a dramatic difference. Not that I don’t also want to swap an LQ4 in my ride…

My house is at 7600', and we usually go up to Denver at 5280. I'm wanting to go to Lake Powell before it turns into a small pond but I need to get over Eisenhower Tunnel which is over 11000' and Vail Pass.

 

[Teamwieland]

I do like the gears idea, although I've got 3.73s already. Since my motor has almost 230k on it already, it's got to be getting a little tired as a lot of those miles were pretty tough. I've got a line on a few LQ4s already and think it makes sense to try that route first. On a 4x4 I have to think a gear swap is at least $2-3k.

 

[Teamwieland]

I just looked up the towing capacity for 2003 GM full size vehicles. Interestingly, the main difference in capacity, whether 5.3 or 6.0, or 1500 or 2500, is rear axle ratio. Very little difference (few hundred lbs) between 5.3 and 6.0. Considering my 5.3 should tow 7400 lbs (at or near sea level presumably), getting more power should get me close to where I need to be with the new boat.

 

[adventurenali92]

I just looked up the towing capacity for 2003 GM full size vehicles. Interestingly, the main difference in capacity, whether 5.3 or 6.0, or 1500 or 2500, is rear axle ratio. Very little difference (few hundred lbs) between 5.3 and 6.0. Considering my 5.3 should tow 7400 lbs (at or near sea level presumably), getting more power should get me close to where I need to be with the new boat.

Nice boat setup! She’s a beauty!
I had four GM 6.0 equipped SUVs belonging to the family that I was living with at the time(my youth pastor and his whole family) when I decided to jump into a GM full size. I knew I loved the three Denali Yukon XLs, but my first thoughts were “do I really need a Denali, with the bigger engine?!” So I looked at Z71 package suburbans and SLT package Yukon XLs. Until i went and test drove a non Denali Yukon xl and knew the 5.3 wasn’t gonna satisfy me, especially knowing in my head I was gonna be pulling that sea ray for quite a bit more than I already was. I had driven the three Denali package Yukon XLs previously over the course of detailing them all and already knew the feel of the 6.0, and that was kinda it for me. When I found mine and I was everything I was looking for, that was all there was to it. Lol. Fortunately my Denali was already factory equipped with 3.73 gears.

 

[S33k3r]

If you are going to go through the engine, why not upgrade the LQ4 to LQ9 specifications? I think there are only three components' worth of differences -- pistons, rods, and something I forget. DISCLAIMER: No an engine builder -- I just read a lot. I also forget a lot... :-(

 

[Teamwieland]

LQ9 is higher compression and requires premium.

 

[adventurenali92]

LQ9 is higher compression and requires premium.

This is true. And many will say the LQ4 will be just fine on 87 and there’s no difference whatsoever.

I ran my LQ4 on 87 grade this first year I had it as I didn’t know otherwise. I switched to 91 and my engine runs so much better. I can feel a noticeable difference in power and I actually see better fuel economy on 91. When I had the truck tuned by blackbear he adjusted for 91 octane and it’s even better. Worth the extra fuel expense in my opinion to run 91, especially where power is concerned for towing. Theres my .02 worth. Lol.

 

[Ilikemtb999]

Slap an ss2 cam and pac 1218 springs in there and gain some torque/hp that way as well since you’ll need to tune this anyways.

 

[norcalboon]

My 2003 Suburban with 5.3L has 225k and I just upgraded my boat. 3.73 rear axle. Boat is about 6500 lbs on trailer. Love my Suburban but at 6000 ft elevation I lose about 30% of my power. 5.3L struggles bad with the new boat, especially on hot days and loaded down. Looking at dropping in an LQ4 (salvage or reman) if it will make a significant difference. Not willing to go LQ9 as 85 octane is expensive enough. I know fuel economy will fall off a cliff as my folks have a Silverado 2500 with LQ4, but I'm mainly trying to avoid buying a new truck altogether. Anyone done an LQ4 swap for improved towing?
Also,I bought a 2013 Tahoe this year with the Gen IV 5.3L. After CAI, straight through exhaust, and Diablosport tune, it didn't tow any better than my old Suburban. 5.3 isn't the answer for me at this elevation.

I tow a 7k TT and family of 5 plus German Sheppard all around CA, OR, NV so climb all the hills. Started with a 2005 Yukon XL 1500 with the 5.3 and 3.42. Hills killed me. Upgraded to 2012 Yukon XL Denali - pulls great with the 6 speed, and I really like the auto level. Earlier this year I picked up a 2005 Yukon XL 2500 w/ 6.0 (LQ4) and 4.10s. It also pulls great but needs to be at 4K RPM for max torque - so with the 4L80 I’m in 1st or 2nd gear climbing depending on MPH. The 2500 is the most stable and once in the power band it handles everything no problem, I had to get used to revving that high up long steep grades and I’m 100% stock. The 2500 is at 100k miles so my next plan is new plugs and wires and I would
like to get it tuned, CA doesn’t make that easy. IMO the 6.0 and 6.2 do the job just fine - both around 8-10 MPG while towing. I’m sticking with the 2500 to tow in my case to limit the wear on the Denali.

 

[NardDog]

LQ4 will get it done based on my experience towing fifth wheel trailers in the mountains. However the 4L60e won’t be up to it. Better anticipate a trans too.

Exactly, the engine and tranny - Drivetrain need to both be up for the task, 4l80 be the way to go.

 

[Teamwieland]

Ok so considering dropping in an LQ4 6.0. Found a few locally that are Gen III, in the ‘02-04 year range. Can I reuse my harness and ECU? Also will my exhaust manifolds work as well?

 

[S33k3r]

I'd talk to the engine builder if I were you.

 

[Mudsport96]

Ok so considering dropping in an LQ4 6.0. Found a few locally that are Gen III, in the ‘02-04 year range. Can I reuse my harness and ECU? Also will my exhaust manifolds work as well?

The ecm will work..but.
You will need a tune, no way around that.
Yeah it will run, but it will be far from optimal and will get worse mpg and less power than currently... if you dont hurt the engine. At minimum a crank relearn will need to be done.
The exhaust manifolds will work, but i think the 6.0 manifolds had a larger outlet along with a larger overall size system. Yours will work, may look into a whole 6.0 system in the future.

 

[steiny93]

I've owned a few 5.3's and 6.0's towed many loads around the 6k lb size (boats / rv's / jeeps).

I don't know how much of a difference you'll get out of just an engine swap. On paper the 6.0 is better but not significantly better, say 15% improvement (saying this with the thinking that at altitude you are calling for power at speed, so the better torque curve of the 6.0 isn't really helping that much, rather you are in need of greater upper end torque). I bet swapping the gearing would give you more noticeable improvement then going to a 6.0.

Boost will help the most at altitude (like crazy help), if you dig you can find chargers on the secondary at decent numbers.

 

[S33k3r]

I've owned a few 5.3's and 6.0's towed many loads around the 6k lb size (boats / rv's / jeeps).

I don't know how much of a difference you'll get out of just an engine swap. On paper the 6.0 is better but not significantly better, say 15% improvement (saying this with the thinking that at altitude you are calling for power at speed, so the better torque curve of the 6.0 isn't really helping that much, rather you are in need of greater upper end torque). I bet swapping the gearing would give you more noticeable improvement then going to a 6.0.

Boost will help the most at altitude (like crazy help), if you dig you can find chargers on the secondary at decent numbers.

He says he doesn't want to run premium fuel.

 

[Mudsport96]

He says he doesn't want to run premium fuel

Boosted or not, premium fuel is a decent idea when towing.
My dad always ran low grade in his 2002 6.0 2500hd always. Once we had to run to pick up my cousins truck in Minnesota with the trailer. About halfway back on a fuel stop the station was having pump problems and only could sell 93 premium. Needless to say dad was pretty pissed bit my cousin was reimbursing him so a tank of 93 it got.
Never again when towing did he use anything but 93 octane. He said he could feel it pull better.
And after seeing how the timing tables work with knock tables and calculations with doing a little playing with tunes, ill bet it did. Running 85-87 can easily put you in the low octane timing table if the ecm sees knock pulling upto 8 or even 10 degrees of timing. That could be as much as 20 hp and just as much tq. 93 octane when towing has the potential knock resistance to keep the truck in the high octane table and not lose power if loaded down more than usual. Anyone towing a decent load needs to run a tank of premium even if the vehicle doesn't specifically call for it.
But in the long run, even with a 6.0 4.10s are needed in mild to medium hilly areas. If he is foothill/mountain towing he really should go to 4.56s.