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Discussion Starter · #1 ·
My dealership sells its own dealer-modified "Duramax SS," a 2500 HD Crew Cab with the Allison 5000-series transmission. This example is a black 4x4 LS, which hardly mattered to me, and I really don't need to comment on the rest of the truck. It's big, it's bad, and it's really wacky goofy buttery fun.

The guts of the conversion, is a performance chip (I still don't know which) that allows the Duramax to snort out 400 hp and a grotesque, writhing, cyclopean 690 lb-ft of torque. I don't know of any other mechanical modifications, but if there are, I'll follow up with them.

As you all know, a 2500 HD Crew Cab 4x4 is huge, but that kind of power makes it go, in a really REALLY (sic) manner. It feels about as fast as a 1500 SS (low sixes to sixty) off the line, and much quicker at speed. Stomp the gas at 65 mph, and, after a brief delay as the Allison upshifts, you get a solid kick in the turd-slicer. You can race against a lot of stuff in this, and win.

Very though it may be, this tuner's acceleration is still weird, as it still redlines at about 3000 rpm. It almost feels like the Allison is doing the accelerating, while the engine just sits there, CVT style. The low first gear dulls the standing start, but the rest of the ratios really make stuff happen.

For a behemoth, the 2500 HD's stiff chassis makes it feel pretty good, like a 6000 lb skull and crossbones. The recirculating ball steering does what it's supposed to do, and it has very little play. Cornering ain't much, especially since the wheels and tires are stock (this is still a 4x4), but the new (for 2003) brakes feel really good, and the real fun in driving this truck is in lighting the afterburner coming out of a corner.

According to our techs, the drivetrain is more than up to the 690 lb-ft of torque going through it. Say that a few more times, and 690 lb-ft of torque keeps sounding like more and more, even though it's actually still 690 lb-ft of torque. GM agrees, enough that this tuner still carries the full factory warranty at least. I'm not sure I'd ever want to put this in 4x4 low though.

Now that I'm geeked, I'd really like to see this truck done as a 2x4 regular cab, maybe even a dually, with the ZF 6-speed. Clunky though it is, by car standards, it might make this an even more stupid, fun ride.

The verdict: what Cthulhu would drive.

Ghrankenstein
 

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Discussion Starter · #2 ·
The chip on this conversion was the Hypertech Power-Programmer for diesels.

Party on down.

Ghrank
 
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