Originally Posted by Thelt
My best guess at this for my 2012 is that traction flows like this:
2wd default mode (VSC on) minimum traction mode meant for times when traction is not an issue.
2wd VSC off Auto LSD on better traction that activates stronger limited slip for the rear differential. Nice for times when you need a little more traction but do not want to go to full 4wd.
4wd TRAC off four wheel drive with open differentials on both ends
4wd default mode (TRAC on) four wheel drive with limited slip on both differentials.
I am not sure what happens in 4lo.
IF this is the case, than the major difference seems to be in H4 (4WD-HI) in that you say the standard mode is open differentials or no traction control (TRAC OFF). On the 2009-2011 Tacomas the standard mode when you go into H4 is TRAC ON (no engine output regulation, same as AUTO LSD).
To have open diffs. or no traction control in H4 (or H2), you must stop the vehicle and press and hold for a few seconds, the VSC OFF BUTTON (truck with wavy lines below). Lights come on to let you know. Now, if you push that button again or restart the truck, you go back to the standard TRAC ON mode.
IN L4, only the OFF ROAD TRD has traction control, but it is a whole level stronger than TRAC, and is called A-TRAC (A=Active)... and instead of just limiting the non-traction tire's spin, it stops it... matching the rotation to the opposite tire, the same as done with a locker.
The big difference between A-TRAC and a locker is:
1) A-TRAC works on all 4 tires, unless you have the rear tires locked, then it only works the front tires.
2) A-TRAC is automatic in that it only locks up a spinning tire when it looses traction and not constantly. This is why A-TRAC does not affect steering ability as lockers do. You can leave A-TRAC 'on' any time you use Low Range... and it just remains on standby for when you loose traction, and only works then.
3) Another difference is because A-TRAC is automatic, the tires will occasionally spin as it checks to see if control is needed, while allowing you to make tight turns easily. The locker-only fans see this as a weakness, as their lockers don't allow any free spinning on one tire.
In the end, the A-TRAC vehicle makes it to the same location as an equivalent vehicle (same type tires, ground clearance, driver skill) with front and rear lockers, as we have seen in numerous Moab and Baja and other photos, videos. A-TRAC and a rear locker are standard features on 2009+ 4WD OFF ROAD TRD TACOMAS.