In a Yukon? That'd be an interesting weight distribution issue. 1000 lb engine in place of what's probably a 500 lb engine. I think you'd need some suspension changes!
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One thing I'd also wonder about with these torque numbers pushing 900 is what sort of lag you get and how much you can realistically use that torque. I suppose when you're towing going down the road and get an incline is where you'd see it mostly in not having to downshift. That said, with the 600 lb-ft I had in my '04, I don't recall ever having to downshift. However I wasn't towing huge trailers with it like
@denverpilot does. Normally just set the cruise at 70-85 and went down the highway.
On the Yukon, the guy who I saw who did it, left the stock Chevy transmission in it, and knew that it would die eventually... haha. It did. During a prolonged burnout. DeBoss Garage on YT. Fun stuff he does. There's a series of about ten videos of the process. He didn't do any suspension work. But it wasn't a 5.9 Cummins either as I recall. It was a smaller one. Like their new crate engine, but I'm sure his was used out of something else.
On the towing and the torque/HP wars, that's why I like watching the real world towing tests like the TFL guys. They're slapping 20,000 lbs of trailer behind the trucks and hitting that hill, and all the trucks have essentially tied at the top for a loooong time now. So the bigger numbers are kinda meaningless ... unless they get cut off by a slow vehicle.
In fact... that may be something the need to add to their test next to even make it interesting. Halfway up the hill, hard braking to 30 MPH like they got cut off and then they finish the hill as per normal. Then you might see a difference.
I can pull that hill with 12,500 and not slow down much if at all, but the 5.9 without any computer changes to add fuel and boost, wouldn't keep up with the trucks that they test pulling 20,000 lbs.
I temp limit out on EGT on that hill even with the bigger turbo and plenty of air moving. But I'm conservative on the EGT. My alarm goes off at 1300, and fuel limiter kicks in at 1350, and get out of it or downshift. (I believe the Cummins book says 1350 for three minutes, but I would have to go look. I just don't push mine that hard. If the alarm goes off and I'm not just about to the top of the hill... I get off it or shift it.)
The best part about any of these diesels in the mountains, towing, was the first time you did it and realized you now had a turbo! LOL. (The EcoBoost Fords weren't lit back then...) The gassers without turbos just get lethargic up there. The driving technique for those is really boring. Floor it and watch water and oil temps. LOL.
Towing with the diesel up there, it's fun to watch the looks on people's faces in heavily loaded four banger cars as you're passing them with the truck and trailer behind. LOL.
Someone at the airport yesterday had a brandy new 2017 Dodge and was waiting for someone in the Denver Jet parking lot. All black. You'd have liked it Ted. Haha. And man, I went over and talked to him because it was QUIET at idle. That 6.7 is neat. He rolled his window down and we chatted about his truck for a couple of minutes and unlike mine, he didn't have to shut it off to hear me! Hahaha.