I kept the stock gearing in place. Getting a 10 speed behind that engine would have been amazing too. I am curious to hear more about the driving experience of OP.
L86 to L8T in '19 Yukon XL Denali
- Thread starter chevman88
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Marky Dissod
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Getting a 10L90 behind an L8T, even with 3.08, would've been eye opening, mouth watering, and at times sphincter puckering - but always tragically cool.
@chevman88 What grade of fuel are you running in the L8T? It is designed to run 87, and that is what I ran in mine, but I am curious what your stance is on the matter.
Bigburb3500
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If my 6L90 decides to give up… I’ve been messaging with PowertrainSwap about the 10L90 being able to be used. “In theory” it should all work. I am highly curious about OPs driving experience too!
I'm with you 100%, but per a few posts up, it seems the bell housing pattern is slightly different on the LT motors vs the LS's that you and I have in our 3500's. I don't believe the 10-speed was ever mated to an LS from the factory.
Bigburb3500
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Just because it didn’t come from the factory doesn’t mean it can’t be done! Don’t rain on the parade. The truck really needs 1 more OD gear for non-towing duties on the highway. Would bring up my MPG avg 1-2.
I agree it would make a great package if it’s possible! I’m also a fan of the venerable 6.0. It’s likely to outlive me!
Marky Dissod
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6L80's 4th: 1.152 . . . 6L80's 5th: 0.852 . . . 6L80's 6th: 0.667 . . . 6L80's biggest mistake: lacks a direct drive.
Blame Ravigneaux & LePelletier?
8L90's 6th: 1.000 . . . 8L90's 7th: 0.845 . . . 8L90's 8th: 0.652
10L80 7th: 1.000 . . . 10L80 8th: 0.854 . . . 10L80 9th: 0.689 . . . 10L80 10th: 0.636
However, unless you have a lil plug-in to disable Engine Confusion, see 10L80 9th.
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Bigburb3500
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If I am reading this correctly, the final ratios in the 8 and 10 speed would bring down the RPMs cruising down the highway. With 4.10s at 70-75mph I’m at 2200-2400RPM (iirc). The truck gets much better MPG when below 2k RPM - as in 1-3MPG better based on digital display.
Marky Dissod
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The next-to-final and final gears of the 6L80 & 8L90 are pretty damn close to the same,
and 8th and 9th of the 10L80 are pretty damn close to the same too.
If you can take advantage of 10th (can keep the TCC locked) and downshift to 9th as rarely as possible,
yes, it can be worth a few MpG.
However, if you cruise at a high enough road speed, the 10L80 MIGHT vacillate between 9th & 10th?
Which I guess would still be better than just 9th?
Oh, by the way:
more to come ...
Marky Dissod
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4L60's 3rd: 1.000 . . . . . . . . . . . . . . . . . . . 4L60's 4th: 0.696 . . . (5 speed manuals, woefully underappreciated)
6L80's 4th: 1.152 . . . 6L80's 5th: 0.852 . . . 6L80's 6th: 0.667 . . . (too bad 6L80 lacks a direct drive gear)
8L90's 6th: 1.000 . . . 8L90's 7th: 0.845 . . . 8L90's 8th: 0.652 . . .
10L80 7th: 1.000 . . . 10L80 8th: 0.854 . . . 10L80 9th: 0.689 . . . 10L80 10th: 0.636
In other words, 4L60's last gear ≈ 6L80's last gear ≈ 8L90's last gear ≈ 10L80's 9th gear.
In other words, only 10L80's 10th gear meaningfully improves highway MpGs -
in conjunction with direct injection at several thousand psi, 5W20 motor oil, newer ATF,
and Engine Confusion, which many of you are forced to disable by avoiding 10th entirely,
if you can't disable it with a plug-in.
6L80's 4th: 1.152 . . . 6L80's 5th: 0.852 . . . 6L80's 6th: 0.667 . . . (too bad 6L80 lacks a direct drive gear)
8L90's 6th: 1.000 . . . 8L90's 7th: 0.845 . . . 8L90's 8th: 0.652 . . .
10L80 7th: 1.000 . . . 10L80 8th: 0.854 . . . 10L80 9th: 0.689 . . . 10L80 10th: 0.636
In other words, 4L60's last gear ≈ 6L80's last gear ≈ 8L90's last gear ≈ 10L80's 9th gear.
In other words, only 10L80's 10th gear meaningfully improves highway MpGs -
in conjunction with direct injection at several thousand psi, 5W20 motor oil, newer ATF,
and Engine Confusion, which many of you are forced to disable by avoiding 10th entirely,
if you can't disable it with a plug-in.
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Bigburb3500
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They might be close but the truck cruises so close to the sweet spot. I’m high jacking this thread so I’m going to stop, but we can continue this back on the 3500 thread.
CMoore711
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I know. That’s a diamond in the rough, but it would be ideal to find a K2XX with lifter failure that someone wants to dump instead of fix.
13 MPG isn’t great, but it’s not terrible. That being said 13 MPG of regular unleaded 87 octane is leaps and bounds better than 13 MPG on 91/93 Premium fuel.
I’m sure your mpg will get better as you get the tune dialed in.
tooleyondeck
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Well I don't think anyone bold enough to do this swap cares about MPG, that's why they make the Traverse lol
It's only a matter of time until someone throws one of these in a single cab Silvy/Sierra, if they haven't already, make a mean little truck.
Still running 91, I figure after the dyno I'll decide whether or not to drop back to regular, which for me is 85
.Had to bump back the date to next Tuesday due to scheduling conflicts, but I'm pretty stoked. It drives pretty good as is, but getting it fine tuned should make it feel much better.
As far as mpg goes, the extra torque makes it hard to keep my foot out of throttle, so I'm ok sacrificing a bit and the wife tends to agree
. The reliability alone was worth the swap to me.Be mindful of oil consumption issues. Before and after my L8T swap, I followed a few GM HD forums where owners would discuss oil consumption. I changed the oil in my L8T every 3000 miles. Perhaps a little excessive, but seemed like a small price for peace of mind. I didn't have any notable oil consumption issues with my L8T, but then again, I sold the vehicle after about 14,000 miles on the swap.
Marky Dissod
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Fixed it for you.
1. If you change your oil every x,x00 miles, and you get 0.5Qt of oil consumption (or more, duhr),
change your oil 500 miles sooner next time.
2. Repeat step 1 until you get UNDER 0.5qt of oil consumption, then stick with that interval.
A. If y'feelin froggy, and you get NO oil consumption at all, change your oil 500 miles later next time.
B. Repeat step A until you notice oil ANY consumption. If you get 0.50Qt or more of oil consumption,
see step 1.
Step C3. Install a catch can.
Direct injection engines spray fuel into the combustion chamber at ≈150Atmospheres,
compared to 3 or 4 atmospheres for Gen3 or Gen4 V8s.
Until the piston ring gaps get smaller, SOME of that fuel is going to end up in the crankcase,
which is the major cause of oil consumption in an otherwise properly working engine.
Here's the results, I did ask about octane and even with the lower compression they recommended staying with premium. I figure the extra few bucks per fill is fine by me. They did end up pulling some timing out as it wasn't making any additional power. Another thing to keep in mind is I'm at 4500', if you're at sea level you should see better results.
They said the 10l80e sees about 20% drivetrain loss so crank hp/tq is about 426/500
They said the 10l80e sees about 20% drivetrain loss so crank hp/tq is about 426/500
Marky Dissod
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Even for those of us whose spark maps are not specifically written to take advantage of higher octane,
the cost of 'premium' is recoup'ed in cleaner more thorough combustion /
lower combustion chamber deposits, and less rings friction against the cylinder bores over time.
Everyone should (have been) break(ing) in their 'brand new' engines using premium,
before switching back to 'regular' after the break-in is complete.
