Torsen T-3 question

[ToyotaDan]

On Torsen's web site, under the FAQ section, they mention that using their torsen diff, if a wheel is up in the air, and there is no friction multiplier, nothing happens to the other wheel (wheel with friction). This issue was resolved in torsen T2r. I checked that the 4th gen 4runners have the t-3 Torsen differential. Does this mean that t-3 is just as good, where a spinning wheel will not affect us?

Or do we still need to use the parking break trick when the wheel is spinning?

Thanks!

 

[swimmer2361]

If one wheel on the rear axle is off the ground then ATRAC kicks in and breaks the wheel off of the ground causing more resistance to the wheel off the ground, so more power is diverted to the wheel on the ground.

 

[Kmvreter]

Or do we still need to use the parking break trick when the wheel is spinning?

As swimmer2361 said, ATRAC is the modern version of the parking brake trick. Cycling the ABS to stop the free wheel when it detects spin causes traction to the other wheel. This also applies to the front wheels in 4x4. Since the front's don't have a parking brake to use as a trick the system is actually better than open diffs. I haven't heard the term "parking brake trick" in years but that's how you did it before traction control.

Isn't technology wonderful (now let's see the comments fly and give Koz a reason to eat popcorn...)

 

[Thai]

ToyotaDan,

That is a good question. Remember, we're talking about a center differential, not a rear diff. Therefore, the "parking brake trick" would NOT work on a center diff. But, the concept of this ONE weakness of Torsen diff applies anywhere.

The solution to your problem is...LOCK THE CENTER DIFFERENTIAL when off-roading.

The Torsen T-3 is your center diff. So, in theory, if let's say your rear axle is immersed in mud while your front axle is on dry land. The rear axle has no traction whatsoever over both rear wheels. (Remember, ATRAC only works left and right...it does NOT transfer power front and rear....in this case, since both rear wheels are spinning/slipping equally in mud, ATRAC will not do much in the rear.) In THIS case, the Torsen CENTER diff will send power to the rear axle due to what you read above (power gets routed to the axle with zero traction/friction). This is a rare situation while off-roading. However, this is yet another reason to lock the center differential while off-roading. When you lock the center diff, you overcome this deficiency of the Torsen by forcing power to go equally to the front and rear axles.

Why do you need to lock the center differential (CDL) beyond what i said above:

1: ATRAC requires a certain minimal wheel rotation speed to work. If you are moving very slowly, it won't do much. Backing slowly down a steep hill is one scenario where ATRAC does not work well.

2: If you have an electrical failure that takes out the system, or take a stick in a wheel sensor harness, you are stuck. With a CDL you can regain much of the lost traction.

3: If you break a driveshaft U joint, you are stuck - your rig will go nowhere under its own power. With CDL you can lock the center diff, remove the offending shaft, and attempt to drive out of the woods.

4: If you want to add limited slip or locking diffs in the axles for improved low speed traction (see #1) then they won't be effective without a CDL.

5: ATRAC is hard on the brakes and the differential spider gears. A CDL helps by reducing the workload on the ATRAC.