No problem!! I didn't really understand/believe how it worked until I actually tried it out...... A-Trac can be used in the mud, in rock crawling, or any other situation when you may not be in conditions where all four wheels can get the best traction, or even when you're doing terrain where not all 4 wheels are on the ground at all times. DO NOT USE ON ICE OR DEEP SNOW!! The power dissapation/braking when you DO finally get traction can really do some damage to your drivetrain.
First thing, first. So our FJ's come with a 2-speed transfer case meaning you have 4H and 4L. A-Trac, much like your e-locker, can only be used if you are in 4L.
A-Trac works like this. Without A-Trac, if one wheel (in mud/in air) is spinning on an axle, then the other wheel (on dry land/good traction area) LOSES it's torque because power is routed to the wheel with least resistance (in mud/in air). Why? Because the wheel spinning just spins faster, and the side THAT does have traction is losing torque, so it can't help pull you through. Now, with ATRAC, the ABS sensors will sense this slippage and apply the brake to the spinning wheel. It will apply the brake UNTIL the two wheels are spinning at the same speed...it will apply the brake to slow the spinning wheel to the same speed as the wheel that actually has traction. By doing this, it tricks the differential into thinking that the slipping wheel has good traction...thus, preventing all power from going to the slipping wheel. It evens out the torque distribution to both wheels. This prevents the wheel with traction from losing torque. As a result, the FJ will have power to move your forward. IMO, its the next best thing to having a front locker that forces both wheels to spin at the same rate, much like the rear differential lock does.
It take some getting used to the first few times you use it. When you're up on three wheels, or lose traction in the mud it may feel the same as it does when the ABS engages EVEN THOUGH you're hitting the gas. This is because the A-trac is engaging the brake on the wheel that is slipping even though you're trying to accelerate and pull yourself through.
I've used it several times out here in Colorado on steep trail sections with rocky terrain, and I LOVE it!!! Couple it with rear-diff lock, and there's very little terrain you can't make it through......Ground clearance turns into the limiting factor more than you're drive-train!! :rofl: I've actually had mine in situations where I felt A-Trac kick in when I was on two wheels (getting ready to pitch over a rock or crest) and the brakes engaged on the left front and right rear wheel or vice versa at the same time. Its pretty cool!!! Shy of the crawl-control and KDSS on the LandCruisers and the new 4Runner Trail, its one of the most advanced/best offroading systems you'll find stock on a vehicle with IFS!! :rocker: ......granted, its still not as good for crawling as something with a straight front axle and/or front locker, but, hey......
Hopefully that makes sense, and I didn't slaughter how it works in my explanation too much. If anyone else wants to take another crack at it, please do!
:cheers:
