The 4x4 Caravan

by Lennard Sihlis

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THE 4x4 CARAVAN The 4x4 Caravan is a project under construction near Sundre, Alberta, Canada. I first thought of the concept when deciding what to do with my old Toyota pickup after I blew the motor. The truck had 320,000 km on it and was a rust bucket. So, I decided to combine the rough terrain capability of a built up four wheeler with the ultimate practicality of a minivan. The project consists of parts and pieces from many different vehicles of different years. The main components are as follows:

THE TOYOTA CHASSIS I stripped and cleaned up the Toyota pickup frame. The frame was lengthened 9 inches to fit the Caravan body. New front and rear springs with a 2 inch lift were purchased from Northwest Offroad Specialties in Bellingham, Washington. New front and rear sway bars were also mounted. Double shock mounts were fabricated for the front axle. The Toyota axles were overhauled and reinforced. New 5.29/1 ratio axle gears were installed as well as Detroit Trutrac differentials front and rear. The tires are 35-12.50R15 Khumo mudders on 15 x 8 inch steel spoke wheels.

INTERIOR BODY MODIFICATIONS The Caravan body was stripped of everything except the windshield. As I checked the body to frame fit, I determined that the rear floor would have to be raised 4 inches to clear the frame. The rear wheel housings also needed to be widened and lengthed to clear the big tires. I enlarged the wheel openings in the front fenders also. Because of the larger tires, the wheelbase is stretched longer than the original van. The original body mounts were cut off the frame and new brackets welded on to bolt to the suspension mounts on the Caravan body. The bulbous protrusions inside the engine compartment which mounted the original Macpherson strut front suspension were cut out and replaced with flat sheet metal to gain extra space.

A 4.3l V6 out of a 1993 Chevrolet Astro van was obtained from a wrecker. Many accessory pieces such as throttle body and computer were purchased with the engine. As the Toyota transfer case and four speed transmission were to be used, an Advance Adapters aluminum bellhousing, Chevy flywheel, 10 1/2" pressure plate and custom clutch disc were obtained from Modern Moters 4 wheel drive shop in Calgary. A custom bushing was machined to fit a Toyota pilot bearing in the Chevy crank. The engine was positioned in the frame to allow the transfer case to retain its original bracket. Motor mounts were fabricated and welded to the frame.

INSTALLED ENGINE The stock cast iron exhaust manifolds did not fit because they exited directly in line with the frame rails on both sides. It would be a hopeless search to find any aftermarket exhaust for such an unusual application, so I decided to make my own manifolds out of steel plate and pipe fittings. They are a tight fit but they look pretty good. The exhaust travels through a Y pipe to the catalytic converter and muffler and exits just in front of the left rear tire.

I utilized the fuel tanks from both donor vehicles. The Caravan tank is flat and square, so I positioned it between the frame rails behind the rear axle. The Toyota tank fits inside the frame on the passenger side of the vehicle. It hanges kind of low, so it should have some protection. Both tanks are filled from the stock Caravan fuel filler via custom plumbing. A high pressure electric fuel pump designed for EFI applications was installed inside the frame near the tanks. A dual tank selector valve with twin inputs and outputs allows the fuel return line to function.

The power steering was accomplished by the use of a Toyota steering box and GM pump connected by custom hoses. The fit of the steering shaft was too tight to go straight, so I routed a triple jointed shaft around the power brake booster supported by a bearing on a bracket welded to the shock tower.

I obtained a radiator from a vehicle with Chevy 305 V8 and installed it on fabricated brackets. The whole sheet metal area in the front of the Caravan body where the original tiny radiator was installed had to be cut away. Radiator hoses from other applications were adapted to fit. Engine oil cooler lines are plumbed into the radiator.

The clutch linkage required some planning and about three tries to get it working. The cable from the Caravan's clutch pedal moves a lever which activates a hydraulic master cylinder mounted in the engine compartment. A brake line then runs down to the clutch slave cylinder mounted on the bellhousing.

I had to buy a complete set of GM service manuals to obtain the electrical wiring information I needed to splice the engine wiring harness into the rest of the system. I mounted the engine control module under the dash on the passenger side of the vehicle. Most of the wires could be ignored, but basically the only ones I needed were to supply power to the computer, the two fuel injectors and the fuel pump. The fuel pump is controlled by the computer through a relay. I was quite surprised how easy it was and how well it works. The engine starts quickly and runs smoothly.

SWING-AWAY TIRE CARRIER Sturdy bumpers have been fabricated to provide protection to both ends of the van and secure towing points. Receiver tubes with stabilizer tabs will be installed front and rear to allow a portable winch to be attached. A swing away spare tire carrier from a Bronco II is mounted at the rear of the vehicle. Pipe guards along the sides of the body will double as steps.

FUEL TANK GUARD Underbody armor will include some skid plates. Since the forward fuel tank is exposed below the bottom of the frame, some protection is required. I fabricated a guard that encloses the fuel tank. It is angled on the front to provide some deflection in case of contact with an obstacle. The skid plate bolts to the crossmember at its front end and to the fuel tank mounting bracket at the rear.

Many other small modifications and adaptations have been done such as the parking brake linkage, speedometer cable, battery tray, etc. If you have ever attempted such a conversion, you know that each one of these items can be a challenge in itself.

Well, the project is still far from finished at the rate I work. I don't plan to repaint the whole van; just the panels where body modifications were done. It's not going to be a show vehicle. I intend to use it as a daily driver when all the bugs are worked out. The project has been a lot of fun and work so far and I look forward to the day it's on the road.