Hey all,
To further clarify above:
1. Once you are in 4HI, you are in FULL-TIME 4wd. This is why the 4Runner's 4wd system is so great...so darn flexible! Remember the MULTI-MODE 4WD system is still the same as those found on pre'01 models...it is indeed FULL-TIME once in 4wd. IN FACT, you can leave the 4Runner in 4wd FOREVER! This is something you could NOT do in pre-'99 models (before multi-mode 4wd).
2. With the incorporation of the ATRAC, there was NO need for the rear Toyota electric locker (available on 4Runners prior to 2001). Why do you need it?? ATRAC provides pseudo-limited-slip differential for front AND rear axles.
ATRAC is equally effective as any limited-slip differential. However, it is not as effective as a pure locker.
ATRAC actually does NOT transfer torque side to side as explained by Toyota brochure...it PREVENTS one wheel from losing total power. Let's look at one axle only.
If one wheel is on ice and the other is on dry land, then the wheel on ice will spin. The wheel on dry land will have no power. Why?? Well, power/torque flows to the wheel with the LEAST resistance...thus, it flows to the wheel on ice. Ok, so what does ATRAC do?? ATRAC uses ABS sensors and looks at the speed differences between the two wheels. Since the wheel on ice is spinning faster than the other wheel, ATRAC applies braking power to that wheel...slowing it down to the same speed as the other wheel (THAT is it's goal). By doing so, you are increasing resistance to the spinning wheel...thus, allowing engine power to now flow equally to the other wheel (since both wheels have equal resistance). Thus, in theory, the maximum power one wheel gets is 50%...never 100%. Thus, it prevents the wheel with traction (dry land) from losing power.
For more info on ATRAC, please see:
http://www.toyota-4runner.org/showth...&threadid=5036
3. When off-roading in rough terrain or mud, you need to LOCK the center diff because it turns OFF VSC. Because, if you are stuck in mud, VSC may interpret your attempts to get out as oversteer/understeer (especially if you are sliding back and forth). Therefore, it WILL cut power (dethrottle). With VSC off, ATRAC can function with full engine power to get you out. Thus, you can spin all four wheels! I have seen this on my brother's Lexus LX470 and Discovery. THAT IS WHY YOU LOCK THE CENTER DIFF, among other reasons!
4. You can be in 4LO and not have your center diff locked. Again, this may be pointless in some situation (crawling, etc.), but great for towing (as stated above).
And best of all, ATRAC is active all the time...on dry land, rain, snow, mud...any surfaces!
For 4th gen 4runners, please see this thread:
http://www.toyota-4runner.org/showth...?threadid=2388
Thanks.
