I have a 2005 4Runner w/ V-8 and fulltime 4WD (the selector switch only has 4 hi and 4 lo). I've owned the truck for less than a year and love the way it rides. This is the first "modern" 4WD that I've owned and I'm a bit confused how the traction control/stability system works. I was in a situation over the weekend where I was in some heavy mud and ruts. When I tried to "power thru" the slop, the traction control/stability system took over and would not let the wheels spin and "powered down" the engine and applied the ABS. In my older trucks and Jeeps that I have owed, I would have just blasted thru the muck and kept the wheels spinning. Can I override the system? Is that what the button on the left side of the dash (that I originally thought was a differential lock) does? The truck didn't come w/a manual. All this may sound stupid to you guys out there that have been driving these new 4WD's that supposedly "think" for you, but it's frustrating to us old guys that know how to countersteer! Thanks for anyone's help.
4WD operation
- Thread starter jlkoko
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CJ3Flyr
Super Moderator
Welcome!:frog:
The 4wd is fairly simple. The electronics overlay that makes the T4R pretty darn capable is a more complex alphabet soup of ABS and engine management.
Your T4R has VSC, Trac and ATRAC. I am going to give you a quick summation and some links...
-VSC: There's a gyro that in conjunction with a steering angle sensor and wheelspeed sensors detects skids/slides. Once skid/slides occurs the brakes and engine output are activated/modified to correct the skid.
-TRAC: This detects wheelspin and reduces the engine power in an attempt to regain traction. Secondarily the ATRAC will usually activate too.
-ATRAC: This function applies the brake on the spinning wheel in an effort to redirect the torque to the other side of the vehicle. (Assumption being there will be more traction available.)
What you're encountering is intervention by 2 of the 3 (TRAC & ATRAC). Ideally, in the mud, you don't want intervention from the TRAC or the VSC as either one will cut the engine power. The ATRAC is a good thing for the most part as it provides your right-to-left limited-slip functionality. Ideally there'd be a way to defeat the TRAC & VSC on the '05. Beginning in '08 they put a switch. Pre '08 you have two options: 1) Lock the center differential. The downside is you must be on surface with less traction than a wet, paved road or you'll promote excessive wear and strain due to driveline binding. When the center diff is locked with the switch just to the left of the steering wheel, the VSC & Trac are overridden and turned 'off'. In addition to the center diff lock light you'll see a VSC off annunciation. 2) Install a "Mickey Mouse, work around", VSC defeat switch (link in my sig).
When the center diff is locked (or my VSC off switch is engaged) only the ATRAC works allowing full engine power at your command. Good luck! And BTW, you said mud
:worthlesshttp://www.toyota-4runner.org/showthread.php?threadid=12
http://www.toyota-4runner.org/showthread.php?s=&threadid=5036
http://www.toyota120.com/forum/showthread.php?t=25
:cheers:
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Thanks!
Chris,
Thanks for your very informative description of the process. I understand now what's going on and know that the center diff lock switch is the key to the whole thing. Follow up question........is there a time lag between pushing the VSC button and when the VSC cuts out (or is overridden), or is it immediate? Thanks again.
Chris,
Thanks for your very informative description of the process. I understand now what's going on and know that the center diff lock switch is the key to the whole thing. Follow up question........is there a time lag between pushing the VSC button and when the VSC cuts out (or is overridden), or is it immediate? Thanks again.
CJ3Flyr
Super Moderator
"Time Lag"? Are you referring to pushing the center diff lock button or my VSC off switch?With my VSC off switch it's virtually instantaneous. 2-3seconds at most. The time delay when pushing the center diff lock switch varies a bit, IIRC. The internal gears must get in the correct postion, lock and "report back" to the system that the center diff is indeed locked*. Once the report is recieved it shuts down VSC/TRAC. You can see the process by watching the lights. Flashing lights = in transition, steady lights = cycle is complete. Once the diff lock light goes steady it's a 1-3second delay, same as my switch. The variation in time comes with how long it takes to complete the mechanical aspect of the diff lock cycle.
* That's what the VSC off mod does... It grounds the wire sending the "locked" signal to the controller even though the center diff ISN'T locked. It tricks the system.
:cheers:
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Chris,
I was talking about any time delay for the center diff lock switch. In my situation (trying to make an uphill turn in a muddy/rutted grass parking lot) I guess the best thing to do is press the diff lock switch as soon as I went off of hard pavement and into the wet/slick grass. Your VSC off mod looks fairly simple......it looks like all it entails is a ground wire w/ a switch in between the ground and the VSC control.
Jeff
I was talking about any time delay for the center diff lock switch. In my situation (trying to make an uphill turn in a muddy/rutted grass parking lot) I guess the best thing to do is press the diff lock switch as soon as I went off of hard pavement and into the wet/slick grass. Your VSC off mod looks fairly simple......it looks like all it entails is a ground wire w/ a switch in between the ground and the VSC control.
Jeff