outahere Posted October 4, 2008 Share Posted October 4, 2008 .................The Symmetric system on the 5MT is not that bad. It has static 50-50 bias, and a limited slip rear diff on the GT. A bit basic, but quite effective............ That pretty much sums it up. Basic, simple, reliable, slow response time. The center viscous coupling is capable of full lock up (aka hump mode), when it gets hot enough. Link to comment Share on other sites More sharing options...
outahere Posted October 4, 2008 Share Posted October 4, 2008 ............Viscous diffs rely on heat to work, the heat thickens the viscosity of the oil/fluid in the LSD element, and strengthens a fluid coupling between the axle shafts, somewhat like a torque converter................ Viscous diffs rely on speed differences, and the resulting shear stress in the fluid, to transfer torque. Heat only comes into play to get into "hump mode" (full lock up). See: http://gkndriveline.com/drivelinecms/export/sites/driveline/downloads/datasheets/Viscous-engl.pdf Link to comment Share on other sites More sharing options...
aigochamaloh Posted October 4, 2008 Share Posted October 4, 2008 My 09 2.5i SE 5MT is just the standard symmetric system with a 50/50 split correct? It does have VDC, which only controls engine output and brakes independent wheels to stop spin, is that correct? I keep thinking my car would not fare as well as the car in the video when it had all four on 'ice'. Link to comment Share on other sites More sharing options...
IwannaSportSedan Posted October 5, 2008 Share Posted October 5, 2008 Viscous diffs rely on speed differences, and the resulting shear stress in the fluid, to transfer torque. Heat only comes into play to get into "hump mode" (full lock up). See: http://gkndriveline.com/drivelinecms/export/sites/driveline/downloads/datasheets/Viscous-engl.pdf You are correct, by being more precise. But shearing stress in the fluid creates heat energy, and I would think that sort of heat and shearing stress would build up when such a differential were installed between the front wheels that steer. Link to comment Share on other sites More sharing options...
IwannaSportSedan Posted October 5, 2008 Share Posted October 5, 2008 My 09 2.5i SE 5MT is just the standard symmetric system with a 50/50 split correct? It does have VDC, which only controls engine output and brakes independent wheels to stop spin, is that correct? I keep thinking my car would not fare as well as the car in the video when it had all four on 'ice'. Yes, I believe that all 5MT subarus have symmetric AWD with a static 50% split, at least the ones made in about the last decade of model years. VDC, vehicle dynamics control, controls some braking activity to preserve traction, and limits throttle under certain circumstances. It does not have the Variable Torque Distribution functions of the automatic transmission, and the 6-speed manual, which contain a different center differential, as far as I recall. Link to comment Share on other sites More sharing options...
fishbone Posted October 5, 2008 Share Posted October 5, 2008 Just wanted to reiterate the fact that when we say "symmetrical awd" it is not referred to the traction split front/back but rather the perfect symmetry of the left and right side of the drivetrain, with equal-lengths drive-shafts. Link to comment Share on other sites More sharing options...
ultimakf7 Posted October 5, 2008 Share Posted October 5, 2008 Just wanted to reiterate the fact that when we say "symmetrical awd" it is not referred to the traction split front/back but rather the perfect symmetry of the left and right side of the drivetrain, with equal-lengths drive-shafts. You sure it's not because the front wheels spin forward and the back wheels spin backwards? Link to comment Share on other sites More sharing options...
Jacks GT Posted October 5, 2008 Share Posted October 5, 2008 You sure it's not because the front wheels spin forward and the back wheels spin backwards? Is this what makes the spec so fast? Link to comment Share on other sites More sharing options...
fishbone Posted October 6, 2008 Share Posted October 6, 2008 And here's another thing that some may or may not know. The 5EAT has front and rear speed sensors, so the transmission knows at all times what the drivetrain/wheels is/are doing. If one of them goes bad ... Front and rear vehicle speed sensors, rear wheel speed sensor abnormal If a fault is detected in either or both of the front vehicle speed sensor and rear vehicle speed sensor, the vehicle speed information received from the ABS unit via CAN communication is substituted for control. This enables normal quality shifting Link to comment Share on other sites More sharing options...
ehsnils Posted October 8, 2008 Share Posted October 8, 2008 I have a 5MT model, but I haven't tested that. But I suspect that it's no big deal. If there would have been a problem with it I would have noticed it on the icy roads that I drive in the winter. Link to comment Share on other sites More sharing options...
sajohnson Posted October 19, 2008 Share Posted October 19, 2008 I wonder how well the viscous locking center diff on the 5MT models would do in the bump test with front wheels on rollers... Hi, I'm here doing research for a thread that I started over at http://www.nasioc.com, about the AWD system in my WRX. This is my firt post here but I have been a NASIOC member since 2001. I own a 2002 5MT WRX and I can tell you that it absolutely would not budge with the front wheels on the rollers. The front wheels would spin all day long -- it acts almost like it has an open center diff. I have done a bunch of testing of the VCU based AWD system in my car and I can say unequivocally that the VCUs are extremely weak. If anyone's interested, the link to my thread over at NASIOC is: http://forums.nasioc.com/forums/showthread.php?t=1617957 BTW, I read through this entire thread and found it very interesting an informative. I'm in the process of checking out the links that were posted. I also came across the "Tech Reference" thread here which was very useful: http://www.legacygt.com/forums/showthread.php?t=585 Link to comment Share on other sites More sharing options...
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