Thinking on LQ9 swap Tahoe

[redhat]

Thinking about grabbing a 380tq) for my Tahoe.

The OE LM7 (5.3, 295hp/335tq) was pulled from this Tahoe when it had about 215k on it. It was replaced with a LR4 (4.9, 280hp/295tq) that was a free motor I had sitting around.

The little 4.8 has done admirably all these years, but man is it SLOW. Lots of little tiny grades near me has the 4L60 constantly unlocking the torque converter and or shifting to 3rd gear. If I'm on the NYS Thruway coming home, going westbound, it will downshift to 3rd trying to maintain 70mph. Even worse, it shifts all the time with the A/C on in the summer. Sometimes it'll even go down to 2nd. Just not enough power. The LM7 5.3 was probably the smallest you'd want in one of these trucks with a 3.42 gear.

LQ9 would be quite a nice jump in power. I cannot imagine that this 6.0 would get any worse than a 4.8 always having to scream to maintain speed. Would be an easy swap and can slap a factory cal. on the P59 controller in the truck.

Those of you that have Caddys with them, whats your mileage like?

 

[clinebarger]

LQ9's can be difficult to find, GM likely made 10 times as many LQ4's.

My dad has a 2003 Tahoe with a LQ4 out of a 2006 Express Van & it moves pretty well.

The only difference between the 2 is the compression ratio, Installing a set of 243/799 heads on a LQ4 will result in the same 10.1:1 CR as a LQ9.

 

[andyd]

Please post progress whatever you do

 

[redhat]

LQ9's can be difficult to find, GM likely made 10 times as many LQ4's.

My dad has a 2003 Tahoe with a LQ4 out of a 2006 Express Van & it moves pretty well.

The only difference between the 2 is the compression ratio, Installing a set of 243/799 heads on a LQ4 will result in the same 10.1:1 CR as a LQ9.

I have been looking for stock torque curve charts to decide between the two TBH. I am not looking for top of the rev range power. Nor am I racing. More so that low end grunt. Basically three things come to my mind.

- Better power with 1/4 throttle driving where 1-2-3 is shifting at most 2,300rpm.
- Doing 55mph kick-down to 3rd and that torque around 2,300rpm.
- Overall, not needing the thing to be breathing at 4k to go anywhere (AKA I have to Scream this 4.8 to have any good grunt).

What do you think? Prob a LQ4 would do all that without the need for a LQ9? Plus the LQ9 would prob pull some timing if I kept it on 87? Which I'd prob plan on running.

Like I said I wish I could easily find some some torque curve charts. And I think I do remember your post a while back about that Tahoe, gotta go find it now.

 

[4WD]

Looks healthy at 3k anyway

 

[redhat]

Please post progress whatever you do

Will def do.

 

[SubieRubyRoo]

Why not toss like a 62mm turbo kit on the 4.8? it would give it way more torque than anything that ever came stock, wouldn't significantly impact highway mileage, and could likely be done for less than an LQ9/LQ4 swap can?

I know you're not looking for peak power, but Richard Holdener did a build a few years back with a H/C/I 4.8 and a 76mm turbo and the thing made over 1200HP on the stock bottom end. It will handle a turbo just fine...

 

[Bottom_Feeder]

Maybe stick a new cam in it first?

 

[97K15004WD]

Why not toss like a 62mm turbo kit on the 4.8? it would give it way more torque than anything that ever came stock, wouldn't significantly impact highway mileage, and could likely be done for less than an LQ9/LQ4 swap can?

P59 ECM in this video

 

[redhat]

I think even with a potentially boosted 4.8 I'd prefer a 6.0 for the low end torque. I've owned two Ecoboosts and would prefer that torque you get from tip-in throttle versus the "Kickdown- turbo spool, and then power".

Me personally I'd rather swap a motor than put together a turbo kit or install one. On3 probably makes one?

 

[JavierH19]

I like the power of the lq9 6.0 and l87 6.2 but i wish both my Yukon XL Denali and Escalade esv had 5.3's like my sierra instead. More efficient and for what they're used for ie long road trips and regular family hauling performance isn't needed. I'll take the efficiency.

 

[SubieRubyRoo]

I think even with a potentially boosted 4.8 I'd prefer a 6.0 for the low end torque. I've owned two Ecoboosts and would prefer that torque you get from tip-in throttle versus the "Kickdown- turbo spool, and then power".

Me personally I'd rather swap a motor than put together a turbo kit or install one. On3 probably makes one?

You’re comparing at least a 6 speed, possibly even 10 speed, to the 4L60. You’re not going to get all kinds of downshifts because there’s limited ratios; if you’re keeping the same trans, the 4.8 will provide much more torque (and that’s why I recommended a small turbo… ) so that it’s much more biased to provide grunt from idle-4000 or so and taper gracefully towards redline, whereas a 70mm or bigger would work the whole RPM range but be a little more sluggish down low.

Also, even if you took the 4.8 with identical turbos to the Eco, you’ve got nearly 30% more displacement which will spool the turbo earlier and harder, especially when both manifolds are channeled into a single turbo. On3 may have something.

 

[clinebarger]

I have been looking for stock torque curve charts to decide between the two TBH. I am not looking for top of the rev range power. Nor am I racing. More so that low end grunt. Basically three things come to my mind.

- Better power with 1/4 throttle driving where 1-2-3 is shifting at most 2,300rpm.
- Doing 55mph kick-down to 3rd and that torque around 2,300rpm.
- Overall, not needing the thing to be breathing at 4k to go anywhere (AKA I have to Scream this 4.8 to have any good grunt).

What do you think? Prob a LQ4 would do all that without the need for a LQ9? Plus the LQ9 would prob pull some timing if I kept it on 87? Which I'd prob plan on running.

Like I said I wish I could easily find some some torque curve charts. And I think I do remember your post a while back about that Tahoe, gotta go find it now.

Yeah.....LQ9's don't like regular unleaded.

In my opinion, A LQ4 would fit the bill nicely.

 

[4WD]

IMHO… 4.8L’s need 3.73 … my 2010 5.3L had 4.10 with the 4L60e … Pretty strong hookup…

 

[clinebarger]

I like the power of the lq9 6.0 and l87 6.2 but i wish both my Yukon XL Denali and Escalade esv had 5.3's like my sierra instead. More efficient and for what they're used for ie long road trips and regular family hauling performance isn't needed. I'll take the efficiency.

I never found 5.3L's to give better fuel economy than a 6.0L, Putting a 5.3L in a heavier vehicle.....MPG might get worse.

BTW....Your '05 Yukon Denali doesn't have a LQ9, But a LQ4, Same with the Hummer H2........ Escalade, Sierra Denali, & Silverado SS got the HO LQ9. There where also Vortec Max Silverado's late in the GMT800 cycle.

That's why I say LQ9's are harder to come by than most people realize as the Escalade was the only model made in large quantities & for a few of those years......2wd Escalades got LM7 5.3L's

 

[clinebarger]

P59 ECM in this video

The fact they're brickable if you "Write Entire" is a concern with P59's.....I've only bricked one & it was because the battery voltage was low. I run a P59 in my Camaro & it's been written over 30-40 times.

 

[JavierH19]

I never found 5.3L's to give better fuel economy than a 6.0L, Putting a 5.3L in a heavier vehicle.....MPG might get worse.

BTW....Your '05 Yukon Denali doesn't have a LQ9, But a LQ4, Same with the Hummer H2........ Escalade, Sierra Denali, & Silverado SS got the HO LQ9. There where also Vortec Max Silverado's late in the GMT800 cycle.

That's why I say LQ9's are harder to come by than most people realize as the Escalade was the only model made in large quantities & for a few of those years......2wd Escalades got LM7 5.3L's

Ah you're right about the engine code. But the 5.3 gets at least 1 mpg more and sometimes 2 but i almost never haul anymore and if i do it's for short distances. Mostly highway cruising but I'd prefer to have taller gears with the 6.0 too. 3.73 is a bit high. I'd happily take a lower 2.73 when cruising at 85.

And I've been heavily considering getting my rear diff swapped for a taller one and maybe removing the intermediate shaft, front diff, cv axles, and put 2wd hubs on it. I'm not sure the latter is worth it but what's your opinion.

 

[clinebarger]

Your pick-up is 2wd?

 

[Snagglefoot]

What about the ECM and associated sensors. Is there a kit to purchase in order to make this possible?

 

[redhat]

What about the ECM and associated sensors. Is there a kit to purchase in order to make this possible?

All sensors, locations and wiring between all Gen III LS is the same; and every GM truck/SUV that came with a Gen III LS will have wiring/locations and be looking for the same sensors. All motors externally are the same in regards to longblock. For your destination vehicle you have to use the correct oil pan (truck, Hummer, F-body, etc.) and intake if you have cowl or hood clearance restrictions. Potentially dipstick or oil fill maybe if it's going in some sort of Van or maybe Isuzu truck?

For a motor swap, I will probably just get new OE sensors for everything while it's out. Easy to get to everything x10.

For ECM, super easy. Can copy the engine calibration between vehicles pretty easily for most vehicles.