GM LT-8 6.6 liter Truck Engine. New for 2020.

Round bales here get hauled by virtually every sized truck out there … and I have seen what they can do when they let one go (not a good day for the old lady's fence) Fortunately the bigger CAT hoes are puled by Mack's … still a popular on/off road truck here.
 
Originally Posted by P10crew
Originally Posted by Dinoburner
Engine capacity, transmission and rear gearing make this test irrelevant.
EXACTLY!
True, but the real problem here is that Chevy did it to themselves, they brought a toy knife to a gunfight. They don't have any other options you could check to make the fight more fair. Chevy doesn't off any other rear gear than the 3.73, the 6 speed is the only transmission while the competition is bringing 8 - 10 speeds. Just to prove how poor of a setup this is, at the end of the video where the chevy is getting bogged down to 2500 RPM it's in 2nd gear, it bogs down to 2500 RPM because the ratio gap between 1st and 2nd gear is huge 4.03 vs 2.36 if it would have down shifted any earlier it would have immediately needed to upshift again due to redline rpm, which would put the truck in an endless upshift/downshift battle which would be even more annoying. If chevy wants to give up the truck market completely to ford and dodge they are doing a good job by bringing trash like this to the market and asking consumers to pay the same price as several other better working options. Chevy: why are you so stingy with the 10 speed? Variations of the 10 speed are already living behind much more powerful engines than your brand new 6.6 liter. Why the 3.73? You at least put 4.10 behind the 6.0. Also, as a side note, why does the dashboard look like you pulled it out of a 89 Caprice Classic? You'll only be able to move these trucks with heavy discounts when the fords and dodges come better equipped for about the same money.
 
Originally Posted by 4WD
What ? No King Ranch PSD farm truck with a huge Yellow Fin and 3 x 400 HP Merc Verado's … oh, and the Farm Truck plates to prove it, LoL ...
Oh Ya!

yellowfin-36.jpg
 
Originally Posted by Tman220
You'll only be able to move these trucks with heavy discounts when the fords and dodges come better equipped for about the same money.
That's probably who GM is targeting with these - price-point shoppers and construction/utility fleets who just need a basic truck that can haul a decent amount for the jobsite. I don't live in the country where you see trucks haul horse trailers, bales of hay or heavy equipment - but I do see XL/WT level trucks haul equipment, tools and supplies for the jobsite. The utilities would love a base-level truck and slap a utility body with a cherrypicker on it. I'm sure any competent mechanic can swap in a different gearset, it's a off-the-shelf Dana or AAM axle but GM didn't want to drop in their new 10-speed. The DMax trucks come with an Allison-branded gearbox that's not a real Allison. It could be a related to the Ford 10-speed. Allison is working on a 9-speed for their 1000/2000 series. https://gm-techlink.com/?p=11703
 
Correction, the 10L1000 isn't related to the Ford/GM 10R80/10L90 series, though I don't see the new Super Duty's 10R140 being related to the 10L1000...
 
I'm looking forward to the 6.6L gasoline engine with the 6 speed and 3.73 gears. I drive thousands of miles in GMC 2500 company trucks with the 6.0L and 4.10 combination. The 2020s and newer will have the bigger crew cab, larger tires, more power and lower rpm which should help fuel economy. Unlike the nincompoops at FLT, I select a gear that will pull a grade at a maximum of about 4,000 rpm and not worry if the speed drops. Don't forget that these are light duty trucks with almost the same HP as big rigs, but limited cooling capacity. On hot summer days, you may not get away with holding your foot to the floor for 12 minutes without overheating the engine then going into limp mode or worse. With my Duramax 6.6L my target is 3,000 rpm ascending, or descending with the exhaust brake. I never let the programming decide the gear, as per owners' manual instructions in the towing section.
 
Originally Posted by userfriendly
I'm looking forward to the 6.6L gasoline engine with the 6 speed and 3.73 gears. I drive thousands of miles in GMC 2500 company trucks with the 6.0L and 4.10 combination. The 2020s and newer will have the bigger crew cab, larger tires, more power and lower rpm which should help fuel economy. Unlike the nincompoops at FLT, I select a gear that will pull a grade at a maximum of about 4,000 rpm and not worry if the speed drops. Don't forget that these are light duty trucks with almost the same HP as big rigs, but limited cooling capacity. On hot summer days, you may not get away with holding your foot to the floor for 12 minutes without overheating the engine then going into limp mode or worse. With my Duramax 6.6L my target is 3,000 rpm ascending, or descending with the exhaust brake. I never let the programming decide the gear, as per owners' manual instructions in the towing section.
I usually select my own gear too. I have never had any heating problems in the 02 or 17 6.0 4L80E/6L90E even pulling Vantage in Washington 10 miles of 4 to 7 percent grades going 60 at anywhere from 3500 to 4500 rpm in 100 degree heat towing 7800 to 8000lbs. The gas trucks are cooled pretty well. The 2017's tranny cooler is awesome compared to even my old aftermarket 40,000lbs cooler. Both of my trucks have/had 4.10 gears. They make a huge difference.
 
Last edited:
How I ever got by with a 3 speed turbo 400 and 4.10 gears behind a 350 sbc or 454 bbc is a mystery. Expect the 10 speed in more vehicles in the next few years as manufacturing capacity increases.
 
Originally Posted by userfriendly
. Don't forget that these are light duty trucks with almost the same HP as big rigs, but limited cooling capacity.
Isn't the issue with heat part of why the 6.0/6.4L PSD as well as Navistar's MaxxForce engines having issues with the EGR and oil coolers? All the 1-ton class pickup diesels make as much HP(if not more) and torque as a 8-9L class engine in a regional delivery truck or school/transit bus application. It's kinda cool and a little scary a pickup can have as much stock HP/torque as a bus or a delivery truck for the local Coke or beer distributor.
 
Originally Posted by ls1mike
Originally Posted by userfriendly
I'm looking forward to the 6.6L gasoline engine with the 6 speed and 3.73 gears. I drive thousands of miles in GMC 2500 company trucks with the 6.0L and 4.10 combination. The 2020s and newer will have the bigger crew cab, larger tires, more power and lower rpm which should help fuel economy. Unlike the nincompoops at FLT, I select a gear that will pull a grade at a maximum of about 4,000 rpm and not worry if the speed drops. Don't forget that these are light duty trucks with almost the same HP as big rigs, but limited cooling capacity. On hot summer days, you may not get away with holding your foot to the floor for 12 minutes without overheating the engine then going into limp mode or worse. With my Duramax 6.6L my target is 3,000 rpm ascending, or descending with the exhaust brake. I never let the programming decide the gear, as per owners' manual instructions in the towing section.
I usually select my own gear too. I have never had any heating problems in the 02 or 17 6.0 4L80E/6L90E even pulling Vantage in Washington 10 miles of 4 to 7 percent grades going 60 at anywhere from 3500 to 4500 rpm in 100 degree heat towing 7800 to 8000lbs. The gas trucks are cooled pretty well. The 2017's tranny cooler is awesome compared to even my old aftermarket 40,000lbs cooler. Both of my trucks have/had 4.10 gears. They make a huge difference.
I'm guessing the 6.6 will eventually make it to the Express. Cooling can be a problem in the Express. I bet Chevy can make it equal to the truck chassis if they tried. Based on the video the 6.6 doesn't look any different than the 6.0 pulling up the grades.
 
Originally Posted by Eric Smith
Originally Posted by ls1mike
Originally Posted by userfriendly
I'm looking forward to the 6.6L gasoline engine with the 6 speed and 3.73 gears. I drive thousands of miles in GMC 2500 company trucks with the 6.0L and 4.10 combination. The 2020s and newer will have the bigger crew cab, larger tires, more power and lower rpm which should help fuel economy. Unlike the nincompoops at FLT, I select a gear that will pull a grade at a maximum of about 4,000 rpm and not worry if the speed drops. Don't forget that these are light duty trucks with almost the same HP as big rigs, but limited cooling capacity. On hot summer days, you may not get away with holding your foot to the floor for 12 minutes without overheating the engine then going into limp mode or worse. With my Duramax 6.6L my target is 3,000 rpm ascending, or descending with the exhaust brake. I never let the programming decide the gear, as per owners' manual instructions in the towing section.
I usually select my own gear too. I have never had any heating problems in the 02 or 17 6.0 4L80E/6L90E even pulling Vantage in Washington 10 miles of 4 to 7 percent grades going 60 at anywhere from 3500 to 4500 rpm in 100 degree heat towing 7800 to 8000lbs. The gas trucks are cooled pretty well. The 2017's tranny cooler is awesome compared to even my old aftermarket 40,000lbs cooler. Both of my trucks have/had 4.10 gears. They make a huge difference.
I'm guessing the 6.6 will eventually make it to the Express. Cooling can be a problem in the Express. I bet Chevy can make it equal to the truck chassis if they tried. Based on the video the 6.6 doesn't look any different than the 6.0 pulling up the grades.
It was 3000lbs more. they tested my truck with 13700ish. I thought they tested the 6.6 with 16700ish.
 
Originally Posted by Eric Smith
I'm guessing the 6.6 will eventually make it to the Express. Cooling can be a problem in the Express.
If GM can make the 6.6 work in the Express chassis, they will have a hit on their hands with the school bus/RV/bread van/ambulance builders who are still buying Express stripped or cutaway chassis. I would imagine the 6.6 needs less cooling than the DMax.
 
A_Harman said:
Originally Posted by Snagglefoot
The Ford has a 4.3 rear end. That was apparent in the conversation at the end of the test. The GM had a 3.73. Apples and oranges. Here are the gear ratios of the Ford transmission: 4.7 2.99 2.14 1.77 1.52 1.27 1.0 .85 .64 The Chev has the 6 speed The ratios were: 4.06 2.37 1.55 1.16 0.85 0.67 From watching the video, the Ford operates in two gears. I believe the guy said the test was run with gears 2 through 5. The Chev equivalent would have been 2 and 3. So with the two trucks in second gear the Ford would have been at a multiplier 4.3 x 2.99 = 12.9 The Chev would have been 3.73 x 2.37 = 8.8 The gearing differed by (12.9-8.8)/12.9 = 32%. They were testing two sets of drivelines. The engines didn't have much to do with the result. Certainly Chevy could do better. Offering something like a 4.11 would be a start. Please go ahead and see if you can confirm which two gears were being used by the Ford. It was cruising at about 5800 rpm, shifted so it was at 4200 then shifted back down to be at 5800 rpm.
You read my mind! I was about to look up the transmission ratios, but you beat me to it. The Ford mostly ran in 4th gear during the climb, as is visible on the gauge cluster. After they got the truck up to speed at the beginning, the driver backed off the throttle, and it upshifted for a little while but couldn't maintain speed in 5th, then went back to 4th. Further into the climb, he had it floored, and the 7.3 roared along at 4800 or so for a long time, then lugged down to 4200. At the very end of the run, the hill gets more steep, and the engine lugged down to 4000, then the trans downshifted to 3rd, bringing the engine speed up to 4600. Then they had to back off after a few seconds as they got into traffic at the tunnel entrance. The GM truck didn't have a gear indicator, so it's tough to know what was going on there. The good gear ratio for the Ford was 1.77 x 4.3 = 7.611 The GM didn't have that kind of overall gearing available. In 2nd, it is 8.84, and 3rd is 5.78. The 'tweener gears that Ford's 10-speed has are key. If the GM had dropped to 2nd, the engine would have had to run at 14% higher rpm than the Ford, and would have been buzzing 5400 rpm most of the time. But the driver would have had the option of backing off slightly to maintain a decent speed. If the GM held 3rd gear, the engine would have been running 24% lower rpm, or about 3600 rpm. This is below torque peak rpm of the L8T, and is probably why it fell flat on its face. Transmission programming for heavy vehicles shouldn't allow the engine to drop below torque peak rpm.
Click to expand...
I drive one everyday, and agree.......they need to offer some granny ratios in the work trucks, maybee even 4.88. I wish my 6.0\6l90e had a 5.11. I think it about fuel economy in a bubble, not in the real world.
 
It isn't 2005 either. Diesel costs $4 a gallon around here and RUG is $2.50, and you've got unreliable emissions controls to deal with on top of the costlier fuel. Mileage is similar. There's no reason to consider a diesel unless you want to tow over 15K lbs.

I'm shopping used heavy duty trucks and have no intention of considering a diesel.
 
Brons2 said:
It isn't 2005 either. Diesel costs $4 a gallon around here and RUG is $2.50, and you've got unreliable emissions controls to deal with on top of the costlier fuel. Mileage is similar. There's no reason to consider a diesel unless you want to tow over 15K lbs.

I'm shopping used heavy duty trucks and have no intention of considering a diesel.
Click to expand...
My current work truck is a 15 gmc 3500 drw 4x4 6.0 gasser. This was my personal truck, until I sold my DMax 3500, and turned it into my daily work truck.....anyway it just broke 80000 miles........Before it life as my work truck, it would generally be used to tow my 5th wheel. (12000 lbs actual) to the beach, in the mountains and so on. There is one pass on 421 in NC westbound toward Boone.........12 miles, 6-8% with turns...........typically takes 8 minutes to go up 8 to go down............i would run my 6.0 @4200 in 2nd, for 8 minutes straight. ATF temp gets to about 220 then stops, all other temps seemingly uneffected. Going down, I leave it in first and scream at 5500rpm, no brakes...........when doing this, the temps actually go down. Seen it for my own eyes while hooked up to my HP tuners VCM scanner.........

Currently, when I tow my excavator (8500 lbs kx91-3 kubota with attachments) it goes on my 22500lbs triple axle goose.........total weight is about 15500 depending on some other factors.........

Sure it is slower than a diesel, but does the same thing......get a diesel hot and watch what happens......not so much with gas.

Point is, people have got spoiled with the power of modern trucks......they literally have too much power in some cases (if there is such a thing). 25 years ago, the highest tow rating for a truck was the GM 7.4 in the 3500hd with 4.56 gears, with a measly 290 hp \ 410 ft lbs, and those trucks are still on the road today, especially for AT&T guys. Gas engines in trucks are made to spin, so spin them! Of course, many people today really dont know how to drive.........

Mostly Valvoline / Napa synthetic used throughout its life thus far, but switching to RP HMX on next service as I despise Valvoline for selling out to the Saudis........
 
eroberts82 said:
My current work truck is a 15 gmc 3500 drw 4x4 6.0 gasser. This was my personal truck, until I sold my DMax 3500, and turned it into my daily work truck.....anyway it just broke 80000 miles........Before it life as my work truck, it would generally be used to tow my 5th wheel. (12000 lbs actual) to the beach, in the mountains and so on. There is one pass on 421 in NC westbound toward Boone.........12 miles, 6-8% with turns...........typically takes 8 minutes to go up 8 to go down............i would run my 6.0 @4200 in 2nd, for 8 minutes straight. ATF temp gets to about 220 then stops, all other temps seemingly uneffected. Going down, I leave it in first and scream at 5500rpm, no brakes...........when doing this, the temps actually go down. Seen it for my own eyes while hooked up to my HP tuners VCM scanner.........

Currently, when I tow my excavator (8500 lbs kx91-3 kubota with attachments) it goes on my 22500lbs triple axle goose.........total weight is about 15500 depending on some other factors.........

Sure it is slower than a diesel, but does the same thing......get a diesel hot and watch what happens......not so much with gas.

Point is, people have got spoiled with the power of modern trucks......they literally have too much power in some cases (if there is such a thing). 25 years ago, the highest tow rating for a truck was the GM 7.4 in the 3500hd with 4.56 gears, with a measly 290 hp \ 410 ft lbs, and those trucks are still on the road today, especially for AT&T guys. Gas engines in trucks are made to spin, so spin them! Of course, many people today really dont know how to drive.........

Mostly Valvoline / Napa synthetic used throughout its life thus far, but switching to RP HMX on next service as I despise Valvoline for selling out to the Saudis........
Click to expand...
You're a man who knows what he wants....
 
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