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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 Sequoia Forum.

What is this discussion about? Toyota Sequoia, Toyota Highlander, Toyota 4Runner, Toyota Land Cruiser, Toyota RAV4, Toyota Tacoma, Truck, SUV

Messages Page 216 of 250

#2142 of 2487 Re: RAV4 .vs. Subaru AWD [hdfatboy] by 2toyotas

Jan 16, 2008 (10:00 am)

Replying to: hdfatboy (Jan 16, 2008 8:49 am)
http://www.tundrasolutions.com/forums/sequoia/29500-2005-sequoia-first-looks/
  
You will clearly see the transfer was changed to the VF4AM which includes the torsen. This info is directly from toyota, your page is not. How can the Sequoia have the same transfer case as the V8 4Runner? The V8 is Full Time 4WD, and the Sequoia has a 2WD option? The VF4BM does also have the torsen in the center diff though. If you spend 10.00 for a day and go on techinfo.toyota.com which is also a toyota site, you can see all the features and how they work. I am not trying to go back and forth with you, but I will make sure you post the correct info. It is not fair to give people the wrong info about a vehicle.

#2143 of 2487 Re: RAV4 .vs. Subaru AWD [2toyotas] by 2toyotas

Jan 16, 2008 (10:51 am)

Replying to: 2toyotas (Jan 16, 2008 10:00 am)
1. General
 The ’05 Sequoia uses the multi-mode VF4AM transfer.
 Along with the adoption of the VF4AM transfer, the transfer lever has been discontinued. Thus, in the
4WD mode, the driver operates the 4Lo switch to switch between Lo and Hi.
 The VF4AM transfer is already in use on the ’04 4Runner with the 1GR-FE engine. For details on the basic
construction and operation of the VF4AM transfer, see the ’03 4Runner NCF (Pub. NoSpecifications 
Model ’05 Sequoia ’04 Sequoia
Engine Type 2UZ-FE 
Transfer Type VF4AM VF3AM
Drive Type Multi-mode
(Part-time & Full time) 
H2 1.000 
Gear Ratio H/H4 1.000 
L/L4 2.566 
Reduction Gear Type Single Pinion Planetary 
Center Differential Gear Type TORSEN LSD*2 Double Pinion Planetary
Oil Capacity
Liters (US qts, Imp.qts) 1.4 (1.5, 1.3) 1.2 (1.3, 1.1)
Oil Viscosity SAE 75W-90 
Oil Grade API GL-5 API GL-4 or GL-5
Weight (Reference)*1 Kg (lb) 41.2 (90.8) 42.8 (94.4)
*1: Weight shows the figure with the oil fully filled.
*2: TORSEN is TOYODA-KOKI-TORSEN’s registered trademark. NCF238U

#2144 of 2487 Re: RAV4 .vs. Subaru AWD [2toyotas] by hdfatboy

Jan 16, 2008 (11:53 am)

Replying to: 2toyotas (Jan 16, 2008 10:00 am)
This discussion is not about fairness. It was about information and sources. I appreciate you sharing the Toyota product brochure for the 2005 Sequoia as that is the first resource of any type that depicts the Sequoia in that year having a VF4AM transfer case. Obviously the other sources were incorrect.
 
The Toyota info you shared does clear the matter up regarding the type of transfer case used in the pre-08 Sequoias. Curious that so many other sources would either be incorrect or would not have referenced that transfer case in the earlier model years.
 
Based on your access to the Toyota site can you clarify which model years the Sequoia, LC, LX470 and the 4Runner each transitioned to a Torsen center LSD from an open center differential?

#2145 of 2487 Re: e [hdfatboy] by wwest

Jan 16, 2008 (12:05 pm)

Replying to: hdfatboy (Jan 15, 2008 8:44 pm)
"..It would make quite a racket after it fails...."
 
No, it wouldn't/doesn't. The spring pre-loaded clutch type, just as would a regular clutch in a stick shift, simply ceases to work once the friction surface has worn off. The VC type might "lock" in failure mode but since it is designed for "failsafe" operation that is rather doubtful.
 
So a driver probably wouldn't notice the failure until the moment of need arises.

#2146 of 2487 Re: RAV4 .vs. Subaru AWD [2toyotas] by wwest

Jan 16, 2008 (12:19 pm)

Replying to: 2toyotas (Jan 15, 2008 10:22 pm)
"..Once you are moving you wouldn't want ALSD (A-LSD) you would want TRAC on to keep stability.."
 
Someone, please, correct this if you have information otherwise but I think I have read documentation indicating that A-LSD is a sub-mode of TRAC. Whereas TRAC's default, always on, mode will instantly apply braking to a slipping wheel and simultaneously dethrottle the engine, if you put the system in A-LSD mode it will allow a certain level of wheelspin/slip just as one might sometimes want to get unstuck.
 
I think, also, A-LSD capability is only to be made available on RWD or R/AWD vehicles.
 
For many years now owners have complained about this aspect of TRAC, no ability to use wheelspin, say for rocking the vehicle back and forth to get unstuck, out of a mudhole, and now Toyota is offering A-LSD as a possible solution. Previously the only solution was to somehow disable VSC/TRAC altogether.
 
"..want TRAC on to keep stability."
 
Methinks you meant to say VSC.

#2147 of 2487 Re: d [trebor129] by wwest

Jan 16, 2008 (12:28 pm)

Replying to: trebor129 (Jan 16, 2008 9:09 am)
"That being said, it has disadvantages to a mechanical LSD in that slip has to occur before it goes into action...."
 
Assuming a VC, Viscous Clutch, implemented LSD is considered "mechanical" your statement is wrong, a VC must experience a period of slippage before it will "tighten" the coupling coefficient.
 
"A mechanical Torsen system.."
 
Doesn't this add to the confusion? I have never considered the Torsen system to be in the LSD "realm", more of a torque control/distribution system rather than an LSD.

#2148 of 2487 Re: e [wwest] by hdfatboy

Jan 16, 2008 (12:34 pm)

Replying to: wwest (Jan 16, 2008 12:05 pm)
I was referring more to a Torsen type which would not operate seemlessly after failure.

#2149 of 2487 Re: d [wwest] by hdfatboy

Jan 16, 2008 (12:42 pm)

Replying to: wwest (Jan 16, 2008 12:28 pm)
Almost all references to the Torsen differential, including the manufacturer's refer to it as a LSD.
 
You description of the viscous liquid diff is accurate and one of the reasons its not the best mechanical design for transfer of torque under severe conditions. It can be ineffective when operating in sand for example in transferring torque from the rear to the front of an AWD vehicle. It excels however at providing a very smooth torque transition when operating on slippery road surfaces.

#2150 of 2487 Re: RAV4 .vs. Subaru AWD [hdfatboy] by wwest

Jan 16, 2008 (12:47 pm)

Replying to: hdfatboy (Jan 16, 2008 8:49 am)
"There is no reference anywhere I've searched that the Sequoia had a lockable mechanical center LSD prior to 2008."
 
I thought the Sequoia ALWAYS had a lockable mechainical center diff'l for 4WD/4X4 mode...??
 
And yes, while that was otherwise an "open" diff''l (or transfer case equivalent) I thought they used TRAC braking in AWD mode to effectively have a center LSD..?
 
And isn't that basically the same system used quite effectively on the RX330/350, the HL and the Sienna AWD systems today, the VC version of those systems having been dropped prior to the '04 model year.

#2151 of 2487 Torsen "C" by wwest

Jan 16, 2008 (12:53 pm)

The way I read all of this is that Toyota has adopted the Torsen "C" center diff'l design so the engine torque to the front would/could be limited to not more that 40%. The "old" system, TRAC braking, could clearly result in 100% of the engine torque to the front driveline therefore quickly converting a reasonably beniegn handing rear torque biased AWD vehicle into a wildly uncontrollable, SCARY, FWD, F/AWD vehicle.

Messages Page 216 of 250

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