6.6 Gas L8T Engine Swap in 2015 Suburban

[Marky Dissod]

Normally I bytcz & whine about 3.73 or 4.10 with 6L80,
but with an L8T, I would not be surprised if it actually gets impressive MpGs with 3.08 ...

 

[L8T BURB]

Yes I have regularly seen 26-28 MPG on 50+ mile drives through rural 55 MPH state roads. Usually brings home 22 MPG at 70 MPH interstate travel.

 

[Marky Dissod]

Yes I have regularly seen 26-28MpG on 50+ mile drives through rural 55MpH state roads.
Usually brings home 22 MpG at 70 MpH interstate travel.

For the sake of clarity and posterity:
22MpG (or better), @≈55MpH, with a 6.6L V8, a 6L80, 3.08 axle, in a 3ton vehicle with the aerodynamics of a box?

Yet the gov'ts of the world have spent BILLIONS trying to convince us that engines need to be smaller?

 

[L8T BURB]

For the sake of clarity and posterity:
22MpG (or better), @≈55MpH, with a 6.6L V8, a 6L80, 3.08 axle, in a 3ton vehicle with the aerodynamics of a box?

Yet the gov'ts of the world have spent BILLIONS trying to convince us that engines need to be smaller?

At full disclosure, my wife has a 2021 Toyota Sienna Hybrid and I have owned 2 other Toyota hybrid vehicles in the past. I love hypermiling in them. A lot of times I will use the same hypermiling techniques in the Suburban, and do not use cruise control. It is a bit of a job, but the MPG returns puts a smile on my face lol.

 

[Marky Dissod]

For the sake of clarity and posterity:
22MpG (or better), @≈55MpH, with a 6.6L V8, a 6L80, 3.08 axle, in a 3ton vehicle with the aerodynamics of a box?

Yet the gov'ts of the world have spent BILLIONS trying to convince us that engines need to be smaller?

At full disclosure, my wife has a 2021 Toyota Sienna Hybrid and I have owned 2 other Toyota hybrid vehicles in the past.
I love hypermiling in them.
A lot of times I will use the same hypermiling techniques in the Suburban, and do not use cruise control.
It is a bit of a job, but the MpG return puts a smile on my face.

In other words, the driver's driving technique is roughly AS important as the choice of vehicle being driven?

(Problem with hypermiling in metro-urban NYC, is NYC - traffic lights make hypermiling almost impossible,
everyone else finishes making it impossible.)
(Problem with hypermiling on the highway, is everyone else INSIDE your vehicle.
Not easy to get them on board with 'pulse & glide', if I remember correctly.)

By the way, when you had your Suburban L8T's tcm tuned, did you bother to tell the tuner that you hypermile?

 

[Bigburb3500]

This is a great build thread! I just purchased an 18 Suburban 3500 with the 6L90 already so I wonder how easy the 6.6L would drop in?

Thanks for posting and good luck with selling. I also agree the Toyota hybrids are pretty great! Too bad our Suburbans are not offered with true meaningful hybrid systems. Oh well.

 

[Marky Dissod]

... wonder how easy the 6.6L would drop in?

No meaningful external dimensional differences between any 4.8L / 5.3L / 5.7L / 6.0L / 6.2L / 6.6L / 7.0L GM Corporate Small Block V8 ...
... physically, as easy as any other GM Corporate Small Block V8. Estimate the physical labour at 2 business days, give or take.

It's the programming that takes extra time.

 

[Bigburb3500]

It's the programming that takes extra time.

Marky, if extra time was my only issue in life I am not sure I would be on this forum… Having enough $$$ to buy the extra time is the issue hahaha
Not sure I can rationalize spending more money after just buying the truck. I will let you know when my $2 scratch off pays off or if the 6.0 gives up the ghost (doubtful).

 

[tooleyondeck]

If you are seriously considering selling this BEAST, you probably have a good shot at getting it featured in a magazine with as many pics/updates you provided on here. I could see this featured in Motortrend, C&D, or Street Truck...

 

[L8T BURB]

UPDATE

I have officially decided to sell the Suburban. I was wanting to get some meaningful opinions on a reasonable list price? My initial thought is $18,000. What do you guys think? I plan to clean it up this weekend and list it on marketplace.

A few highlights below...

2015 Suburban LT (all options that an LT can get w/rear seat screens, leather captains, 2nd row heated seats, moonroof, etc.)
197k miles
2WD
Full RST conversion with 22 inch RST wheels from a 2022 Suburban, RST grille and RST badging throughout

Within the last 10k miles the following has been replaced...

Engine AND transmission replaced with a 5 miles 6.6 liter L8T engine and upgraded 6L90 transmission (swap is well documented in this forum)
New shocks/struts in front and rear
New upper/lower control arms in front
New front wheel bearings
New upgraded custom driveshaft
Rear diff fluid flush
Brake fluid flush
ALL exterior lighting converted to LED

I am likely missing some of the details but I believe this sums it up. Please let me know a reasonable list price. At 18k, I am losing BIG but I am not sure what this thing is really worth, or if its even worth 18k... and its time for me to move on.