Clarification on Fulltime 4wd and Lock with TC

[Evancool]

Ok so I read thru the forum here for info but need a little more clarification:

http://www.toyota-4runner.org/5th-g...ifferential-front-differential-confusion.html

I understand the the VSC deactivates when the Center diff is locked, but what about traction control (TC)? To my understanding that system acts like a quasi limited slip for front and rear differentials while the torsen center has its own limited slip feature.

So does the quasi still work with the center diff locked? i.e. will it still apply the brake to the spinning wheel to transfer power to the other side?

I tend to use the locker in moderate and deep snow which seems to receive mixed feelings on the forums.

Sorry if this has been asked before but couldn't find anything else in my search.

 

[8086bruce]

Mine seems to in 4hi lock but not in 4low lock.

 

[d2huffman]

The traction control is active with or without center diff locked (aplies brake to spinning wheel(s)). When the center diff is locked, the power is equal to front and rear axles. Normal (unlocked) puts power at 40/60. I prefer to lock center diff when ever I am in snow or mud as it reduces wheel spin and gives you a much more possitive response.

 

[JB.]

Well worded description by d2huffman, especially the parenthetical clarification since the term traction control gets used different ways and, in this case, is synonymous with ATRAC.

 

[JB.]

Mine seems to in 4hi lock but not in 4low lock.

Works in low range, too, and actually more aggressively but since power is applied less abruptly in low than in high, it often has less need to engage in the first place when getting started on a slippery surface.

 

[sonerick]

Normal (unlocked) puts power at 40/60.

Under static conditions, the torque split is 40/60 front to rear in 4WD with the center diff unlocked. The cool thing with the Torsen T-3 in our 4Runners, however, is that when unlocked, it continuously varies torque bias based on surface conditions. Thus, when the front wheels slip, up to 70 percent of the power goes to the rear wheels, and when the rear wheels slip, up to 53 percent of the power goes to the front wheels.

See post # 4 here: http://www.toyota-4runner.org/general-discussions/12-01-up-4wd-system-trac-vsc-torsen-t-3-a.html

 

[d2huffman]

Thanks for the expanded info - I didn't have that on the top of my head and didn't want to complicate the discussion at that point. Between the Torsen and TC it is just shy of locking diffs front and back. I agree that it is a pretty amazing system. In driving on main roads in 4H I think it is best to let the Torsen do its thing. Times when you might lock the diff is for going down slick hills in lower gears to avoid slipping and when you want to avoid that initial slipping that makes the Torson do its think. I tend to shift to 4L when I am on FS or back roads, especially if snow or mud as I like to be able to go up or down gears and locking the diff under these conditions gives you greater control.

 

[Evancool]

Thanks everyone! I'm glad to know it still works regardless of lock status. I've never had to use 4-Lo yet, I turned it on once just for the heck of it but immediately turned it back off.

This is changing the subject a bit, but is it common for the diff lock to take a while to engage? I was testing it tonight while driving and it took about 10 minutes of random maneuvering to finally engage. The last thing I did was back up about 20 feet then it finally locked. Sometimes it take a while to unlock too and usually it will make a rough sound like I just hit something then the lock light turns off. I informed the dealership about this but they didn't seem too concerned.

 

[JB.]

This is changing the subject a bit, but is it common for the diff lock to take a while to engage? I was testing it tonight while driving and it took about 10 minutes of random maneuvering to finally engage. The last thing I did was back up about 20 feet then it finally locked. Sometimes it take a while to unlock too and usually it will make a rough sound like I just hit something then the lock light turns off.

No, it should be really quick and easy especially after the first one. A matter of seconds. Sometimes it's almost instantaneous. Were you driving straight while you made the attempts? The loud unlock clunk means the transfer case got wound up a little. Did you make some turns while locked? Not a huge deal if they were just normal, rolling street turns, but you don't want to make a habit of it.

I'd keep working it back and forth (while driving straight) until the operations only take a few seconds, and then keep it exercised by doing it at least once per month. Within reason, you can't do it too often. Use the low range, too.

 

[Evancool]

No, it should be really quick and easy especially after the first one. A matter of seconds. Sometimes it's almost instantaneous. Were you driving straight while you made the attempts? The loud unlock clunk means the transfer case got wound up a little. Did you make some turns while locked? Not a huge deal if they were just normal, rolling street turns, but you don't want to make a habit of it.

I'd keep working it back and forth (while driving straight) until the operations only take a few seconds, and then keep it exercised by doing it at least once per month. Within reason, you can't do it too often. Use the low range, too.

That's what I was afraid of. When I bought the 4R it did do it almost immediately and unlocked quickly too. Yes, I was driving straight during the test and made just usual street turns thinking maybe the teeth weren't lining up to lock. I did have to make one fairly sharp turn for my parking spot but I didn't crank the steering all the way. When turning it jittered like it was locked but the light was still blinking. But after that parking, I rolled it back and forth about 20 feet twice then it finally locked with a solid light.

It's only been used once or twice during winters for the last 5 years. I'll follow your suggestion and exercise the lock and the 4-Lo on a monthly basis. Thanks!