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

[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.