Typically, the conversion takes about 300 hours-or six weeks-but that depends on the source of the drivetrain, whether new or used, and if it's supplied by the customer or the company. Sourcing all the conversion parts takes a couple of weeks, Buff says, and the labor takes another four. The components basically consist of the following:* Fuel lines * Tank floats* Driveshaft* 3-inch body lift * New gauge instruments* Custom air-conditioning lines* Double insulation in the hood and firewall* New tires (285/75R16 Michelin LTXM/S to fill wheelwell)* 4-inch MagnaFlow stainless steel exhaust with 22-inch muffler * Heavy-duty hitch
In addition to pulling out the factory gas engine and dropping in a Duramax/Allison drivetrain, the labor involved includes flushing the fuel tank, reprogramming the engine computer (and sometimes replacing it), and lifting the body to make room for the Allison. The factory diesel cat is enlarged slightly at the ends to accommodate the larger exhaust tubing. And some model years require modifications on the engine mounts.
If the customer supplies a Suburban and a complete diesel donor vehicle, the conversion components (not including the engine and tranny) cost $9,000, and labor is another $16,000. For an extra $3,000, Buff will put the leftover gasoline engine into the diesel donor.
If Buff supplies the drivetrain, he charges $35,000 for a vehicle with a used Duramax setup and $45,000 for a new unit from Detroit. For the used drivetrain, he'll buy two vehicles and swap the engines, and later, he'll sell the one with the gasoline transplant.
21-MPG SuburbanThat all might sound simple in theory, but it's obviously a bit more complicated in practice. Even so, Bub says the results are worth it. Fuel consumption on an 8.1L gasoline Suburban ranges from 8 to 14 mpg, depending on the load, but Buff says a Duramax Suburban can get as much 21 mpg on the highway, lightly loaded, and 15 mpg towing a loaded trailer over the Continental Divide. And the tow rating comes in at an honest-to-goodness 10,000-12,000 pounds-no stress, no strain.
Despite the 900-pound increase in overall weight with a Duramax under the hood, the difference in performance is startling. "That Duramax pushes the Suburban around like it's a Corolla," Buff says with a grin. And that's without a chip, which Bub plans to add later on, along with some other upgrades-a six-inch lift and a conversion to an '04 front fascia.
In the meantime, the factory setup is really smooth, as Bub's wife, Toni, confirms (she's the primary driver of the vehicle). "I feel invincible in this truck," Toni says with a laugh. "I go anywhere I want, and there's no stopping me with all that power." Hey, if a diesel Suburban makes the wife happy, then it's all worth it, right?