The problem with a diesel-powered truck is the commotion from the engine. Sometimes it sounds as if you just wandered onto the range during happy hour at the annual NRA convention. A while back we ventured out in a 1994 Dodge Ram pickup with a 5.9-liter, 175-horsepower, six-cylinder diesel. At idle it sounded as if someone was dropping boulders into a metal drum. So, when Chevrolet offered to park its diesel pickup in the driveway, we accepted with a bit of concern-and a wad of cotton in each ear to cope with the noise. Yet when the 1994 Chevy Fleetside four-wheel-drive, extended-cab pickup arrived-with a 6.5-liter, 155-horsepower V-8 diesel, we quickly found that the concern over diesel racket was unfounded. The Fleetside's V-8 was much quieter than the Ram's six, with the sound more like pea gravel, rather than boulders, being dropped in a metal drum. Once up to cruising speed the diesel quieted even more, as if sand was being poured into that drum. Inside the passenger cabin when traveling at highway speeds, you'd be hard-pressed to tell whether it is a diesel or gas engine under the hood. About the only telltale clue is that the fuel gauge doesn't move often or far with the diesel. When we pulled up to the pump to refuel, however, diesel was 18 cents a gallon more expensive than gas. At least with diesel you get more miles of travel between pit stops. The Fleetside diesel is rated at 15 m.p.g. city/19 highway with four-wheel drive, which compares with a 13/17 rating with the 5.7-liter V-8 in the comparable gas-powered four-wheel-drive truck. Like the Ram, the Fleetside comes with anti-lock brakes, or ABS, but unlike the Ram, you can only get rear-wheel ABS and not four-wheel. Also, there's no air bag in the Chevrolet, which won't have one until the 1995 model year. Ram has one now. While the Ram is a fine truck-except when equipped with a diesel engine-the Chevy pickup boasts a major benefit over the Dodge. The Fleetside has a 3-inch lower step-in height than the Ram, which stands high to foster the bold, macho, big-rig look. The Chevy has easier step-in and slip-out capability. Our test truck was an extended-cab version, which meant room behind the front seat to hold a few kids or several bags of groceries without having to stack them in the rear cargo bed. (The groceries, not the kids. Kids never should be carted in the open back. Cats, yes, but not kids.) However, the truck didn't have power outside mirrors. In such a wide vehicle you need power mirrors, because there's no way to reach the passenger mirror from the driver's seat unless you stop and pull over to the shoulder of the road. A change that needs to be made is in the power window and power door-lock controls. The buttons are next to each other and are roughly the same size. In the dark you may think you're lowering the window but end up u nlocking the door. Chevy needs to redesign the size and shape of these buttons or relocate one to avoid the confusion. The Fleetside started at $18,179. Options such as automatic transmission at $890 and the diesel engine package at $3,670, which includes the engine and twin batteries, block heater and five-year/100,000-mile warranty coverage, brought the sticker to $25,881. Add $600 for freight.