God bless big box retailers. If you walk into a Target or Home Depot and buy a $35 pair of jeans, $150 work boots, or $500 miter saw, you can try on the jeans and boots or rent the tool you want before you decide to drop your dollars on the purchase. And if you buy and decide you don't like them a week or two later, you're getting all your money back or swapping out for a full replacement.

Now, try showing up at a truck dealer with your 15,000-pound double axle fifth wheel and ask to take a new heavy duty out for a spin before you buy. Sorry bub, not gonna happen. The only blessing you'll be doing is a Hail Mary before signing the paperwork. An unloaded, ten-minute surface street and quarter mile highway dash is all you get before making this $50,000 purchase. Got buyer's remorse later? Sure, they'll take the truck back, or trade it, and leave you $5,000 lighter for your business.

Buying a heavy duty pickup is even tougher when the truck is all new or has an all new powertrain - particularly if it's an unproven diesel.

Diesels are the powertrain of choice in HD pickups, going into 70% of the three-quarter-ton trucks shipped in 2006. Historically diesels have been the best motor for hauling because of their superior fuel economy and pulling power versus gasoline engines.

So, many diesel buyers have waited to see how a new diesel will do its first year before driving away with a sophomore unit under the hood or selected a proven competitive choice if they needed a new truck immediately.

But what do you do when all three manufacturers of heavy duty pickups have only new diesel engines to offer in the same model year?

2007 is a historic year for heavy duty pickups. New EPA emissions laws have forced Chrysler, Ford, and General Motors to significantly reengineer their diesel engines to meet the tough new `Tier 2 Bin 5' standards for soot and nitrogen oxide (NOX) output. For buyers, this means the cleanest, most complex and expensive oil burners ever are running under the hoods of every 2007 HD truck headed from factory to farm.

With all the extra equipment necessary to clean the diesel exhaust, would these motors suffer in performance relative to gas engines? Would they run differently under load? Would they suck at hauling?

To find out, we asked Chrysler, Ford, and GM to provide us with six trucks to compare. Three three-quarter-ton, single-rear-wheel, crew cab, four-wheel-drive HDs with gasoline engines, and three one-ton, dual-rear-wheel, crew cab, four-wheel-drive HDs with diesel engines. As we received the detailed specs of each truck, such as equipment levels and axle ratios, we shared that information with the other OEMs, so every manufacturer knew what the others were bringing to the test.

We also asked Ford to let us exercise the all new one-and-one-half-ton F-450. It's the first truck in its class to come from the factory with a standard pickup box.

We hired well-known automotive engineering firm Ricardo Inc. to independently instrument, measure, and certify all of the trucks in our tests. And Ford Motor Company graciously lent us the use of their Michigan Proving Grounds and General Motors loaned us three 10,500-pound trailers for tow testing.

We'll have the second part of our three part feature in the coming weeks. Stay tuned.

Here are the details on the trucks we tested.

Three Quarter Tons, SRW, Gas, Crew Cab, 4WD
2007 Dodge Ram 2500 SLT Quad Cab 4x4
2008 Ford F-250 FX4 Super Duty Crew Cab
2007 GMC Sierra 2500 HD SLE Crew Cab 4x4

TOne Tons, DRW, Diesel, Crew Cab, 4WD
2007 Chevrolet Silverado 3500 LT Crew Cab 4x4
2007 Dodge Ram 3500 SLT Quad Cab 4x4
2008 Ford F-350 King Ranch Super Duty Crew Cab 4x4

TOne and a Half Ton, DRW, Crew Cab, 4WD
2008 Ford F-450 Lariat Super Duty Crew Cab 4x4