Mitsubishi 4x4 Has Heavy Front Axle

MITSUBISHI introduced its model FG four-wheel drive cabover chassis this past fall, said Robert Aquaro, of Mitsubishi Fuso Truck of America Inc in Bridgeport, New Jersey.

Deliveries to Mitsubishi distributors began in September, Aquaro said during a seminar in Las Vegas, Nevada, at the National Truck Equipment Association 34th annual convention. The vehicle is manufactured and sold in Japan and is popular throughout Asian countries, Australia, and New Zealand.

"It has a good market share in those countries down under," Aquaro said. "We don't expect to sell hundreds of thousands of FGs in the United States, but it has a niche audience."

The FG is a Class 3 vehicle rated at 12,000-lb GVW. The front axle is rated at 5,510 lb, which is very high for this type of GVW-vehicle range. The rear axle is rated at 8,600 lb.

The FG is equipped with this axle because Mitsubishi anticipates its use for snowplows. The rear axle assembly has a load-sensing proportioning valve for the rear brakes. Basically all Class 3 trucks use this valve, and it cannot be removed for vehicle modification.

The load-sensing proportioning valve applies rear brake pressure based on the vehicle load, Aquaro said. With heavier loads, more rear brake pressure is applied and less pressure is applied for lighter loads.

Mitsubishi FG Powertrain The powertrain and other components are the same for two- and four-wheel-drive trucks. Both have a turbo charged intercooled diesel engine with direct fuel injection. The transmission is a five-speed manual with a two-speed transfer case.

The FG has the same cab used with two-wheel-drive chassis. The chassis is a bit different because it has camel-back frame rails, which are different than frame rails used on many other chassis in the United States.

The frame rails drop just behind the cab and continue at the same height to the rear of the truck. At the rear, the 32 1/2-inch-high frame is the same height as a two-wheel-drive chassis frame. The frame rails are this shape because FGs built for countries other than the US are available with four-door crew cabs.

The front and rear of the frame have a very high approach angle, making the FG a true offroad, four-wheel-drive vehicle. The FG has a 33-gallon fuel tank.

The four-wheel drive is shift lever mounted on the left side of the instrument panel and steering column.

FG chassis are available in a 109-inch wheelbase with an 85-inch cab-to-axle dimension, which is suitable for a 10- to 12-ft truck body. A 133-inch wheelbase chassis has a 108-inch cab-to-axle dimension for 12- to 14-ft truck bodies.

Mounting Snowplows on FG

Mitsubishi customers have mounted a wide variety of truck bodies on the FG chassis, Aquaro said. Initially following its introduction, the FG primarily has had dump bodies mounted for use by landscapers. Body manufacturers are working with Mitsubishi to develop other truck bodies suitable for the FG. One company has developed a snowplow for use on the FG chassis.

The transfer case assembly is very simple. Mitsubishi could have used an electronic shift control, but chose not to because of the vocational nature of the truck.

The shift control for the transfer case is two-high to four-high, which can be shifted while the vehicle is moving. The FG cannot be shifted into the four-wheel-drive low position while it is moving. The maximum speed in low range is about 40 mph.

The low-range gears provide pull and 67% gradeability, Aquaro said. The front and rear differentials both have a 5.7:1 axle ratio. The rear differential has a limited-slip option, which most customers order. The transmission has an overdrive fifth gear, which provides a .72 ratio.

"The low-range ratio is 64.2:1, which makes this truck a hill-climber," Aquaro said. "It's really made for heavy off-road use with its high approach and descent angles."

PTO Placement on FG Many body builders are concerned with PTO placement and use, he said. A Chelsea PTO is available for the FG. However, the FG has limited space for installation of a PTO-pump combination.

Permco has a small direct-mount pump that is good for an FG chassis with a small dump body, Aquaro said. But this pump combination may not have enough capacity for a larger vehicle such as a wrecker. Chelsea's standard output shaft PTO can be used and is compatible with the Mitsubishi transmission.

Part of the reason for the 5,510-lb front-axle weight rating is because constant velocity (CV) joints are used on the front end, he said. Mitsubishi chose not to use a universal joint because it lacks the needed strength. The CV joint is more expensive but durable, and it enables Mitsubishi to rate the front axle at 5,510 lb.

"We're very happy with this rating," Aquaro said. "It's one of the strengths of the vehicle."

Another unconventional feature is a manual-locking hub system, because customers are more concerned about durability than shift-on-the-run, he said. The hubs can remained unlocked in the summer when four-wheel-drive is not needed often on commerical vehicles.

Truck Body Mounting On a 133-inch wheelbase FG chassis, a distributor mounted a Knapheide 14-ft landscaper drop-side dump body, Aquaro said. The chassis was equipped with a standard scissor hoist and PTO drive. The subframe was mounted on the lower part of the chassis frame, and the body was cantilevered onto a rest on the upper part of the frame. The chassis frame and PTO pump are stradled by dump body long sills 34 inches apart.

"It was a very easy, clean, and simple body mounting," Aquaro said. "The goal was to use a truck body built with standard specifications by a US manufacturer and to mount it without extensive modifications to the chassis or the body."

Lighting hookups for body builders are provided behind the cab and near the taillights, he said. Wiring for lighting hookups is marked with silver labels that identify the circuit. The wires for each connection are wrapped in blue tape, he said. Body builders do not need to splice into any wiring.

Mitsubishi expects a demand for the vehicle from landscaping contractors, wrecker companies, distributors that service oil-fired furnaces, and service contractors in New England states who often purchase trucks with utility bodies. These demands exist primarily because of the truck's four-wheel drive capabilities and maneuverability.

Antilock Brakes Mitsubishi will begin installing antilock braking systems (ABS) on FK Class 6 and FM Class 7 truck chassis beginning with its 1999 model vehicles built in Japan. The trucks will be released in May or June.

Mitsubishi has several opinions about modifications to the wiring harnesses on its chassis, he said. These modifications never involve NTEA members.

"Typically we see three types of wiring harness modifications," Aquaro said. "One is the hacksaw method, another is the hatchet method, and the third is the electrician method where wires are cut and reconnected with wire nuts."

When it comes to ABS, Mitsubishi is concerned about modifications to its wiring harness, he said. One wiring harness carries all the electrical circuits to the rear of Mitsubishi truck chassis. "We don't want that wiring harness cut."

Mitsubishi recognizes that when the wheelbase of the chassis is modified, changes must be made to the wiring harness. An extension wiring harness with a common connector will be available from Mitsubishi dealers for wheelbase modifications. Mitsubishi will provide advice on how to shorten the wiring harness.

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