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March 1998 Nuts & Bolts

U Joint Path Diagram
Rick Péwé
| Four Wheeler Network Content Director
Posted March 1, 1998
Photographers: The 4-Wheel & Off-Road Files

A Different Spin, Driveline Vibration and More

A Different Spin
I have a '95 Toyota 4Runner with the 3.0L V-6, five-speed tranny, stock gears, and rear posi. With 90,000 miles on it, I am preparing to change the clutch. Some friends told me to replace the flywheel with a heavier unit, supposedly to get more torque at lower rpm. I have always thought that lighter is better, so what is your spin on this debate?
Steve Harron
Houston, TX

This is one of those questions where the answer depends on how you use your truck. A heavier-than-stock flywheel will not actually produce more torque at lower rpm, but the extra inertia created will keep the flywheel spinning longer for a given amount of power input, or torque retention. For instance, if you're driving up a long grade and have to shift down before the engine bogs out, a heavier flywheel will keep the truck moving longer due to the increased inertia of the flywheel, or momentum of movement. The only drawback is the extra initial power needed to get the heavier flywheel up to speed; it will take more throttle input and gas to get it going. In addition, the heavier flywheel weight will reduce throttle response, so acceleration from a stop will diminish. Jim Sickles at Downey Off Road (Dept. 4WOR, 10001 S. Pioneer Blvd., Sante Fe Springs, CA 90670, 562/949-9494) specializes in Toyotas and offers a heavier flywheel for 4Runners that need it. According to Sickles, the additional 9 pounds of flywheel weight increases torque inertia for positive clutch engagement without bogging down the motor. This really helps when larger tires are added, and also reduces stalling during slow-speed crawls.

Getting Engaged
Iwas out 'wheeling in my '96 Chevy K1500 pickup and was halfway across a boulder-strewn stream when I got stuck. Even though I had the transfer case lever in four-wheel-drive low range for several miles, I noticed that only the rear tires were spinning. Is there a problem with these trucks, or am I the only one? How can I fix it?
Gregg Morin
Mesa, AZ

All '87-'97 IFS GM 4x4s use thermally activated axle disconnect devices to engage the front tires. When the transfer case is engaged, an electric switch closes, which sends electricity to a thermal unit on the front axle. As the thermal unit heats up it expands and forces a dog clutch onto the axleshaft that engages the front axle. If this unit fails to operate, the front driveshaft spins but power isn't transferred to the wheels and you get stuck. While GM has improved its thermal actuators, aftermarket companies offer replacement actuators that operate with either cable, vacuum, or electric shift. Warn Industries (Dept. 4WOR, 12900 SE Capps Rd., Clackamas, OR 97015, 800/543-9276) offers a vacuum-operated replacement actuator that screws into the same hole as the factory unit. By hooking up a few wires and hoses a much more reliable engagement is afforded, without the need to drill holes or pull cables. Another option is the electric-shift style from Rancho (800/GO RANCHO), which also replaces the thermal actuator. The Rancho unit is basically a big electric solenoid that replaces the factory style and plugs into the factory harness.

Scouting Around
I've been looking for a manual for my '67 International Scout 800 Half Cab, which I bought for 100 bucks. No one seems to have a manual, and I can't even figure out which of the two four-cylinder engines used is in my Scout. Is there a place that knows this stuff and has parts for my truck?
Patrick Bryan
State College, PA

Lucky for you, we do know about Scouts and a source for all your goodies: Giddum' Up Scout (Dept. 4WOR, 3625 N. Stone Ave., Colorado Springs, CO 80907, 719/632-8294). International Harvester is a mysterious breed to most auto parts stores, so going to a specialist is the best thing to do. Giddum' Up Scout has a complete line of service manuals, and the 1,000-page version for your rig will teach you everything you need to know. As far as which engine you have, the 152ci four-cylinder was used through the '66, while the 196ci was introduced in the '67. This means either engine could be in your Scout, depending on its build date. From the outside, the two engines are virtually identical. The 152 was basically an International 304 engine cut in half, and the 196 was a 392 done the same way. Since the four- and eight-cylinder models share similar internal parts, the smaller engine has a smaller bore. But rather than disassemble the engine to identify it, Rod Phillips of Giddum' Up Scout recommends looking at its serial number. On the driver side of the engine at the front of the block is a machined surface facing sideways, about 3 inches high and 1 inch wide. Underneath the actual serial number are some numbers that indicate the type and size of the engine, with 4-152 indicating the 152 and 4-196 signifying the larger 196.

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