Toyota - 4Runner . org Forum - View Single Post - '01-up 4wd System (A-TRAC, VSC) and TORSEN T-3

Thai · 02-27-2003, 09:48 AM

Some people have questioned me: "Why do you need to lock the center differential when Torsen is already full-time??"

If you lock the center diff, you have 50/50 split of power front-to-rear. This also turns off VSC (stability control...aka dethrottling). This will allow the 4-wheel traction control system to manage left-right distribution of power in front and rear axles via applying braking power to slipping wheels. Because VSC is OFF, the engine does NOT dethrottle when slipping in mud, which would be bad.

Front and rear differential are ALWAYS OPEN. Traction control manages the side to side transfer of power.

Torsen center diff is very similar to Torsen rear differential found on many modified off-roading rigs. The most famous aftermarket rear Torsen diff is, Detroit Truetrac. It is GEAR-based (a good thing). On a Torsen REAR differential, if one wheel is completely spinning, the OTHER wheel on the same axle will be powerless (no torque)... Torsen is excellent in all conditions short of this. In such a situation, you need to apply some braking power to get power to the wheel with traction...a common practice among off-roaders is to either apply brake via brake pedal or slowly pull up the e-brake.

Well, the same thing can happen (in theory) to a TORSEN CENTER diff (as seen on Toyota 4Runners and Range Rovers). If the whole rear (or front) axle on the '03 4Runner is completely in deep mud (no traction), then there is a chance that the other axle (in this case, front) will NOT get any power (even thou it is full-time). For these rare situations, the Toyota Torsen center diff is LOCKABLE. In such rare instances, if you lock the center diff, which guarantees 50/50 power split (front-rear), you will not have any problem getting out. One of the beauty of the Toyota Torsen center diff. By locking this, you also disable both VSC (stability control) AND dethrottling feature; thus, allowing you to power out of a mud hole.

This is similar in principle to the rear differential found on the new Jeep Wrangler Rubicon. The Rubicon has a Torsen LSD AND an air locker on the rear axle. Cool stuff!

Torsen diffs are VERY reliable and very quick-acting. It is quicker acting than most other LSD. It is gear-based, so maintenance is very low.

Hope this helps.

02-27-2003, 09:48 AM	#12 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	Some people have questioned me: "Why do you need to lock the center differential when Torsen is already full-time??" If you lock the center diff, you have 50/50 split of power front-to-rear. This also turns off VSC (stability control...aka dethrottling). This will allow the 4-wheel traction control system to manage left-right distribution of power in front and rear axles via applying braking power to slipping wheels. Because VSC is OFF, the engine does NOT dethrottle when slipping in mud, which would be bad. Front and rear differential are ALWAYS OPEN. Traction control manages the side to side transfer of power. Torsen center diff is very similar to Torsen rear differential found on many modified off-roading rigs. The most famous aftermarket rear Torsen diff is, Detroit Truetrac. It is GEAR-based (a good thing). On a Torsen REAR differential, if one wheel is completely spinning, the OTHER wheel on the same axle will be powerless (no torque)... Torsen is excellent in all conditions short of this. In such a situation, you need to apply some braking power to get power to the wheel with traction...a common practice among off-roaders is to either apply brake via brake pedal or slowly pull up the e-brake. Well, the same thing can happen (in theory) to a TORSEN CENTER diff (as seen on Toyota 4Runners and Range Rovers). If the whole rear (or front) axle on the '03 4Runner is completely in deep mud (no traction), then there is a chance that the other axle (in this case, front) will NOT get any power (even thou it is full-time). For these rare situations, the Toyota Torsen center diff is LOCKABLE. In such rare instances, if you lock the center diff, which guarantees 50/50 power split (front-rear), you will not have any problem getting out. One of the beauty of the Toyota Torsen center diff. By locking this, you also disable both VSC (stability control) AND dethrottling feature; thus, allowing you to power out of a mud hole. This is similar in principle to the rear differential found on the new Jeep Wrangler Rubicon. The Rubicon has a Torsen LSD AND an air locker on the rear axle. Cool stuff! Torsen diffs are VERY reliable and very quick-acting. It is quicker acting than most other LSD. It is gear-based, so maintenance is very low. Hope this helps. __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"