nukefission
09-25-2006, 01:56 PM
Provided by user: X569
<i>Disclamier: Do NOT disassemble your VC as I have done, you CANNOT rebuild it. I had an extra differential sitting around, so I decided to cut into it.</i>
The <b>Viscous coupling</b> is an application used in many of the DSM all wheel drive vehicles. The coupling is caused by a special viscous fluid which is inside of a hermetic (sealed) container. In the container, there are numerous plates which are installed very close to each other, with the viscous fluid stuck between and around the plates.
<table border="1"><tr><td align="center"><b><font size="6" face="Arial"><img border="0" src="http://www.zero2blur.com/reardiffVC.jpg" width="533" height="421" align="left"></font></b></td>
<td align="center"><font face="Arial"><img border="0" src="http://www.zero2blur.com/vc.jpg" width="552" height="423"></font></td>
</tr>
<tr>
<td width="50%" align="center" bgcolor="#3366FF"><font color="#FFFFFF" face="Arial">Exploded view of the rear differential</font></td>
<td width="50%" bgcolor="#3366FF"><font color="#FFFFFF" face="Arial">Cut away view of a viscous coupling off of a 1990 Eagle
Talon Tsi AWD</font></td>
</tr>
</table>
<a href="http://www.zero2blur.com/vc.mpg">See a video of the VC in action</a>
The system works when the spinning speed difference of two axles occurs. When one set of wheels tries to spin faster, perhaps because it is slipping, the set of plates corresponding to those wheels spins faster than the other. The viscous fluid, stuck between the plates, tries to catch up with the faster disks, dragging the slower disks along. This transfers more torque to the slower moving wheels -- the wheels that are not slipping. (<a href="http://auto.howstuffworks.com/differential2.htm">Howstuffworks How Differentials Work</a></span>)
The fluid in the disks causes the plates to lock, making both wheels spin equally. This can be considered a basic clutch. In a viscous coupling, this occurs very quickly to prevent wheelspin. To test this theory, jack up the back of your DSM so both rear wheels are off the ground and jack up the front so only one wheel is off of the ground. Then grab one rear wheel and spin it forward. It does not matter how fast you spin it. If the viscous coupling is fully functional, the other rear wheel will spin forward. If it is bad, the other wheel will spin backwards (or opposite from the way your are turning the first wheel).
<div align="left">
<table border="1">
<tr>
<td width="100%"><font face="Arial"><img border="0" src="http://www.zero2blur.com/VCoil.jpg" width="506" height="388"></font></td>
</tr>
<tr>
<td width="100%" align="center" bgcolor="#3366FF" bordercolor="#FFFFFF"><font color="#FFFFFF" face="Arial">Oil inside the VC (thick as honey)</font></td>
</tr>
</table>
</div>
<b>INSIDE THE VISCOUS COUPLING</b>
There are 35 plates in the housing - 18 steel plates and 17 steel plates. 18 of the plates are connected to the left axle, and 17 plates are connected to the right axle. As you can see, the plates have different geometry. There are 18 steel half-rings that lay in between the outer edges of the two.
<a href="http://www.zero2blur.com/vc1.mpg">See a video of me taking apart the VC</a> (not able (and not recommended) unless you cut it apart)
<img border="0" src="http://www.zero2blur.com/vc1a.jpg" width="554" height="415"><img border="0" src="http://www.zero2blur.com/vc2.jpg" width="552" height="416">
The Viscous Coupling is used in many AWD vehicles because it is simple and effective. Unfortunately, they do wear out with time and I do not believe there are replacements for the DSM line of vehicle VC's. Maybe you, the reader, can start your own company making VC's!
<i><b><a href="mailto:andy.rusho@comcast.net">Andy Rusho</a></b></i>
90 Talon Tsi Awd (blue)
90 Talon Tsi Awd (red)
91 Talon Tsi Awd (blue, junkyard bound)
90 Talon Tsi Fwd (red, sold in 2003)
<a href="http://www.zero2blur.com/dsm.htm">www.zero2blur.com/dsm.htm</a>
<i>Disclamier: Do NOT disassemble your VC as I have done, you CANNOT rebuild it. I had an extra differential sitting around, so I decided to cut into it.</i>
The <b>Viscous coupling</b> is an application used in many of the DSM all wheel drive vehicles. The coupling is caused by a special viscous fluid which is inside of a hermetic (sealed) container. In the container, there are numerous plates which are installed very close to each other, with the viscous fluid stuck between and around the plates.
<table border="1"><tr><td align="center"><b><font size="6" face="Arial"><img border="0" src="http://www.zero2blur.com/reardiffVC.jpg" width="533" height="421" align="left"></font></b></td>
<td align="center"><font face="Arial"><img border="0" src="http://www.zero2blur.com/vc.jpg" width="552" height="423"></font></td>
</tr>
<tr>
<td width="50%" align="center" bgcolor="#3366FF"><font color="#FFFFFF" face="Arial">Exploded view of the rear differential</font></td>
<td width="50%" bgcolor="#3366FF"><font color="#FFFFFF" face="Arial">Cut away view of a viscous coupling off of a 1990 Eagle
Talon Tsi AWD</font></td>
</tr>
</table>
<a href="http://www.zero2blur.com/vc.mpg">See a video of the VC in action</a>
The system works when the spinning speed difference of two axles occurs. When one set of wheels tries to spin faster, perhaps because it is slipping, the set of plates corresponding to those wheels spins faster than the other. The viscous fluid, stuck between the plates, tries to catch up with the faster disks, dragging the slower disks along. This transfers more torque to the slower moving wheels -- the wheels that are not slipping. (<a href="http://auto.howstuffworks.com/differential2.htm">Howstuffworks How Differentials Work</a></span>)
The fluid in the disks causes the plates to lock, making both wheels spin equally. This can be considered a basic clutch. In a viscous coupling, this occurs very quickly to prevent wheelspin. To test this theory, jack up the back of your DSM so both rear wheels are off the ground and jack up the front so only one wheel is off of the ground. Then grab one rear wheel and spin it forward. It does not matter how fast you spin it. If the viscous coupling is fully functional, the other rear wheel will spin forward. If it is bad, the other wheel will spin backwards (or opposite from the way your are turning the first wheel).
<div align="left">
<table border="1">
<tr>
<td width="100%"><font face="Arial"><img border="0" src="http://www.zero2blur.com/VCoil.jpg" width="506" height="388"></font></td>
</tr>
<tr>
<td width="100%" align="center" bgcolor="#3366FF" bordercolor="#FFFFFF"><font color="#FFFFFF" face="Arial">Oil inside the VC (thick as honey)</font></td>
</tr>
</table>
</div>
<b>INSIDE THE VISCOUS COUPLING</b>
There are 35 plates in the housing - 18 steel plates and 17 steel plates. 18 of the plates are connected to the left axle, and 17 plates are connected to the right axle. As you can see, the plates have different geometry. There are 18 steel half-rings that lay in between the outer edges of the two.
<a href="http://www.zero2blur.com/vc1.mpg">See a video of me taking apart the VC</a> (not able (and not recommended) unless you cut it apart)
<img border="0" src="http://www.zero2blur.com/vc1a.jpg" width="554" height="415"><img border="0" src="http://www.zero2blur.com/vc2.jpg" width="552" height="416">
The Viscous Coupling is used in many AWD vehicles because it is simple and effective. Unfortunately, they do wear out with time and I do not believe there are replacements for the DSM line of vehicle VC's. Maybe you, the reader, can start your own company making VC's!
<i><b><a href="mailto:andy.rusho@comcast.net">Andy Rusho</a></b></i>
90 Talon Tsi Awd (blue)
90 Talon Tsi Awd (red)
91 Talon Tsi Awd (blue, junkyard bound)
90 Talon Tsi Fwd (red, sold in 2003)
<a href="http://www.zero2blur.com/dsm.htm">www.zero2blur.com/dsm.htm</a>