The Syclone and Typhoon's AWD drivetrains utilize a Borg Warner transfer case which does the 65/35 power split to the front and rear wheels. This is the same transfer case that can be found in the Chevy Astro, GMC Safari, and Oldsmobile Bravada trucks. While these transfer cases are strong and can handle a substantial amount of power, they are not fully bullet proof and are prone to failures. The most common failure that results in broken front axles, split boots, exploded prop shafts, busted front differentials, and low-speed "parking lot jumps" is a LOCKED viscous clutch.
What is a viscous clutch?
The viscous clutch is a type of limited-slip differential that's designed to control the amount of torque (rotational force) sent to each wheel. It uses a thick fluid ("viscous" means "thick and sticky") that's located between a set of plates inside the clutch. When the plates rotate at different speeds (such as when the front and rear wheels are turning at different speeds), the fluid resists the motion, causing the plates to lock together.
Once the plates are locked, the clutch connects the front and rear axles, sending power to all four wheels. This helps to distribute the torque evenly, providing better traction and control on slippery surfaces like ice, snow, and rain.
The viscous clutch isn't always engaged, though. In normal driving conditions, when all four wheels are turning at the same speed, the fluid inside the clutch doesn't resist the motion, allowing the differential to function normally. However, as soon as there's a difference in speed between the wheels (such as when one wheel slips on ice), the viscous clutch engages to lock the plates, transferring power to the wheels with better traction.
BAD VISCOUS CLUTCH TEST
This test can be run with the transfer case installed in the truck or loose on the ground. What is being checked is the torque required to make the viscous clutch slip. While this test is not scientific, or even to a manufacturer's specification, it will identify whether a V-clutch is "Locked" or "Open".
Here are the conditions for the test:
- Input shaft on T-case is free to turn. If installed, put transmission in Neutral.
- Rear output shaft Locked. If testing on an installed T-case, put a bar through the u-joint, and lodge it against the floor or frame to keep it from turning
- The front output shaft is where you will apply the torque for the test. Use a socket on a torque wrench on the front output flange nut. If installed you can guess to applying 40 ft-lbs to a bar to turn the front shaft. One front wheel must be free to turn. Work safely under the truck.
With the socket or torque wrench on the front output flange, begin to turn it:
Count to 12-15 seconds to turn the front output 90º from starting point with 40 ft-lbs torque applied.
Remember: There should be resistance between the front and rear outputs.
If it is very loose or breaks away quickly after torque is applied, the viscous clutch has failed OPEN.
If you can't budge the front output with the rear locked (trans is in Neutral if T-case is in the truck), the viscous clutch has failed LOCKED.
Here's a great video also showing how to test with the transfer case OUT of the truck:
REBUILD KIT
Sportmachines provides a rebuild kit for the BW4472 transfer case for both Syclone and Typhoon trucks. A full rebuild kit is available or the viscous clutch can be bought separately. To see availability and pricing for both kits along with various other drivetrain parts, CLICK HERE.
