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Toyota 4WD systems explained
2487 messages, Last post on Apr 28, 2012 at 12:48 PM
You are in the Toyota Land Cruiser Forum.What is this discussion about? Toyota Sequoia, Toyota Highlander, Toyota 4Runner, Toyota Land Cruiser, Toyota RAV4, Toyota Tacoma, Truck, SUV
#41 of 2487 ggoodwin22 by tonychrys
Jul 25, 2001 (4:19 pm)
Yes. This is one of the reasons I bought a RX300 (VSC and permanent 4WD) for my wife and son to drive everyday. I definitely sleep better knowing the odds are slightly tilted in their favor in case of an unexpected incident.Goto LexusSafety.com for good explanations of Toyota active and passive safety systems.
#42 of 2487 ggoodwin22 by cliffy1
Jul 26, 2001 (11:44 am)
Absolutely this would have helped. The VSC is very quick to respond to both oversteer and understeer. I'm not saying it is impossible to roll one, but it would take much more effort. I've played with this system a good bit and am shocked at how well it responds in slippery situations.#43 of 2487 cliffy1 by crapgame
Jul 27, 2001 (10:47 am)
Ok, I am getting there, although slowly. Assuming I purchased a 4WD Sequoia, my wife would be best off leaving it in 4WD all the time in order to avoid the possibility of the rev-limiter kicking in? Won't this place excess wear and tear in the 4WD components, or does the 4WD only kick in when slippage is detected?Thanks for your time.
#44 of 2487 crapgame by cliffy1
Jul 27, 2001 (2:28 pm)
You certainly can leave it in 4WD all the time. There really shouldn't be much if any extra wear on the system. Remember, the Land Cruiser used the same system but has no option for 2WD use. If excess wear were an issue, Toyota would not have developed this system for that vehicle.On another note, unless you often have loose gravel at the end of your driveway, I'm not sure I would be overly concerned about the rev limiter. If it rains, hit the 4WD button. If you are on a dirt road, hit the 4WD button. Once you are on a major road, turn it off. If this is too much hassle, just leave it on all the time.
#45 of 2487 cliffy1 by crapgame
Jul 27, 2001 (5:39 pm)
OK, I completely understand you now. Seems relatively simple. There are quite a few gravel roads where I live, and my driveway was gravel until about a month ago. I think in my case, the best bet would be for me to tell her just to leave it in 4wd unless she is on one of the highways.Many thanks for your time.
#46 of 2487 crapgame by drew_
Jul 29, 2001 (11:37 am)
You can leave it in 4WD mode even on the highway, especially if you have to make a sudden course correction to avoid something. Just set it and forget it then you won't have to worry about when to turn it on and off.Drew
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#47 of 2487 Driving in High Water by jcnew4whlr
Jul 30, 2001 (3:01 pm)
I was exploring an area near a couple of rivers this weekend, and came to one place on a gravel road with water racing over the road. There were a couple of those tall-wheel 4WD pickups there and I really think with the Sequoia ground clearance I could have gone through. Problem was it was a dead end road so I knew I'd have to come back. Since the river was still rising I turned around.So what's my question? With high water and gravel, what's the best setting on a Sequoia? 4H with gearshift in second? 4L with gearshift in second? 4L all the way in Low? (Seemed like overkill.)
My username says it all---I'm just learning how to do this stuff.
#48 of 2487 highwater by cliffy1
Jul 30, 2001 (3:55 pm)
My answer would be 4 hi. I would think momentum would be important for this and would only shift to low if I got stuck.#49 of 2487 HL post #494, 499 by llofgren
Aug 06, 2001 (4:14 am)
In the Highlander forum, posts # 494 and 499, describe an RX 300, with an AWD drive system (but no VSC) like the Highlander, getting stuck on a ramp with rollers on the front wheels.....this was a demonstration test.I don't understand why the RX 300 got stuck. Shouldn't the viscous coupling in the center diff thicken and kick in to engage the rear wheels?
Les
#50 of 2487 Les by drew_
Aug 06, 2001 (11:26 am)
No, because it's an open differential and cannot be mechanically locked. The viscous coupling limited slip differential tries to "glue" both front and rear driveshafts together to prevent loss of traction. However, when there is little traction up front, the differential sends all of the power to the path with the least resistace, which in this case is the front axle. This system works okay if the vehicle has sufficient momentum, but if you're in low speed conditions and high demand for power the VC will fail to deliver the needed power. High torque transfers and continous use make viscous couplings fail often.Here is a picture for a stuck AWD RX300. Notice the front wheels spinning but the rear wheels stationary. The ramp simulates a slight uphill snow/ice covered grade.
Drew
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