Servicing the new light trucks

Motor,  Jan 2003  by Weissler, Paul

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Things are popping this year in light truck land, with new models and plenty of safety, performance and convenience upgrades for existing models.

For 2003, there's a fresh crop of SUV's (and one truck) from the U.S., Europe and Asia-and Asia doesn't mean just Japan anymore.

The LU.S. offers the new Ford Expedition and Lincoln Navigator and Aviator, GM's Hummer H2 and the Chrysler Group's hemi-powered heavy-- duty Dodge RaIn) pickups. Europe is sending the Volvo XC90 and the British-built (BMW-- powered) Range Rover. Japan has models from its Big Three--the new Toyota 4Runner and Lexus GX 470, the Honda Element and the Nissan Murano. Add the Kia Sorento to the '03 list, which joins the Hyundai Santa Fe, introduced last year. These two Korean products have been changing a lot of minds.

We know there's more in the pipeline, too, with Nissan ready to show us the Pathfinder replacement this month, a new GMC SUV based on the Envoy coming a bit later, plus all-new GM compact pickups and the 2004 Ford F-150. Even Porsche will soon bring its Cayenne SUV to these shores.

The efforts to improve SUV stability are ongoing, of course. Volvo has made the most impressive moves, with its gyroscopic stability control. However, both Range Rover and Toyota/Lexus, with their hydraulic cross-linking of the shock absorbers, also have significant new technology.

So here's a rundown on the newest SUVs and light trucks now-or soon to be-on U.S. highways.

TOYOTA/LEXUS

A brand-new 4.0L V6-Toyota's first all-aluminum truck/SUV engine-is coming for the new 4Runner and its upscale Lexus cousin, the GX 470, this winter. It's a slightly long-stroke engine (94mm bore x 95mm stroke). Combined with variable intake valve timing, it produces 282 ft-lb of torque at 3800 rpm (245 hp at 5200). It's a very lively engine that actually produces more horsepower than the V8 (235), but less torque (the V8 delivers 320 ft-lb).

The V6 block has an open-deck design with siamesed bores, but there's a water passage between them. The cylinder liners are very thin and not recommended for a rebore, so long down the road they'll have to be resleeved. The main bearing caps are held by four "plastic region" (torque-to-yield) bolts from underneath and two bolts threaded in from the sides.

There's a dual oil pan design-a main aluminum casting (for structural rigidity) and a steel pan as a secondary reservoir to provide needed oil capacity. Cheers to Toyota for the oil filter, which is surrounded by a bracket shaped like part of a funnel. Attach a hose to the pipe on the bracket, loosen the filter and the oil flows through the pipe and hose into a drain container.

The clutch-type fan has a thermostatic bimetal valve that provides threeposition control of the silicone fluid valve inside the coupling--off and low and high speeds.

The intake air chamber is a plastic housing with a solenoid valve actuator to provide two airflow paths based on engine rpm. That actuator is laser-- welded onto the chamber, so if it ever needs replacement, we hope there'll be a field service kit that allows you to avoid installing an entire chamber.

The 4Runner and Lexus GX 470 share the same 4.7 V8 and Torsen (torque-sensing) center differential 4WD system, although each has different controls. Surprisingly, the more luxurious GX 470 has the "rugged" 4H-to4L shift lever, while the 4Runner has an electrical control system with a dashboard knob.

The 4Runner/GX 470 cross-linking of the shock absorbers is a diagonal setup, somewhat like hydraulic brakes. Midpoint in the hydraulic line between one front and the opposite rear shock is a "center absorber." When the vehicle starts to tilt, the shock in compression transfers pressurized fluid to the center absorber, and through it to the extending shock, increasing its damping force.

FORD EXPEDITION LINCOLN NAVIGATOR

The two full-size Ford SUVs are all-new models for '03, featuring rack & pinion steering, four-wheel-vented disc brakes and independent rear suspension, with axle shafts passing through slots in the frame, a design pioneered in the Explorer. But there are also lots of technical differences between the Expedition and Navigator.

The Expedition's base engine is the SOHC 4.6L V8, which has the same horsepower as in '02 (232 horses), but a new torque curve that peaks at 291 ft-- lb. However, the engine block is an allnew aluminum casting, and many engine internal parts were redesigned.

The Expedition offers a 5.4L V8, but it's also a SOHC, with a new stiffer and quieter cast-iron block rated at 260 hp, with a reworked torque curve that peaks at 350 ft-lb.

The Navigator has just an iron-block 5.4 V8, but it's a DOHC version rated at 300 hp, also tuned for torque (355 ft-lb at 2750 rpm). Its engine-mounted fan is controlled by an electromagnetic clutch.

The Expedition's suspension is coil spring on 2WD, torsion bar on 4WD, compared with air suspension on all Navigators (but a forthcoming option on Expedition).

The Expedition/Navigator 4WD has a new Control Trac system, which brings a true 2WD position, while also providing all-wheel drive, 4-High and 4Low. In 2WD, the system disconnects at each front wheel hub, not merely at the front axle, so the axle shafts and gears are motionless. That helps improve fuel economy. The wheel hub disconnect is a next-generation version of the Warn vacuum chamber system that had been used on Ranger pickups.