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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 217 of 250

#2153 of 2487 Re: RAV4 .vs. Subaru AWD [wwest] by hdfatboy

Jan 16, 2008 (2:52 pm)

Replying to: wwest (Jan 16, 2008 12:47 pm)
"I thought the Sequoia ALWAYS had a lockable mechainical center diff'l for 4WD/4X4 mode...?? "
 
I thought I knew the answer until 2Toyotas shared information from the "Pay for" toyota website. While the Sequoia has always had a Lockable ctr differential, I thought the addition of the Torsen LSD (in place of an open diff) was new for 2008. He shared information describing a Torsen Ctr Diff in the 2005 model. Therefore I do not know when Toyota transitioned from an open diff to the Torsen LSD ctr diff. for the Sequoia.
 
I was hopeful that 2Toyotas could look at his website to determine what model year the upgrade actually took place. (As well as when the upgrade to the Torsen occurred for the LC, LX470 and 4Runner.)
 
Most external information sources suggest the Torsen was added to the drivetrain for these vehicles in 2008 with the 4Runner getting it earlier. These sources must be wrong based on his review of the Toyota site.

#2154 of 2487 Re: RAV4 .vs. Subaru AWD [hdfatboy] by 2toyotas

Jan 16, 2008 (9:28 pm)

Replying to: hdfatboy (Jan 16, 2008 11:53 am)
The 4Runner was redesigned in 2003 and began using the VF4AM transfer on the V6 and the VF4BM on the V8. Both have the torsen center diff, with the V6 having a 2WD option.
 
The Sequoia used the VF3AM transfer from it's introduction in 2001 until 2004. It has an open center diff. In 2005 the Sequoia started using the VF4AM transfer already in use on the V6 4Runner, which has the torsen. For 2008 the Sequoia is now using the JF3A transfer which also has the torsen.
 
The Land Cruiser/LX470 used the HF2A transfer which has an open center diff. from 1998 until 2007. For 2008 the Land Cruiser/LX570 will use the JF2A which has a torsen center diff. One interesting thing is the Land Cruiser/LX used the HF2AV center diff until 1997 which had a Viscous center diff. They dropped it in 1998 for an open center diff.
 
ATRAC began in the Land Cruiser/LX in 2000, and the 4Runner and Sequoia in 2001.
 
The torsen center diff is definitely an improvement over an open center diff. I had an 03 Sequoia and then traded for an 05, and the big difference is on inclines, with the open diff ATRAC would brake up to 3 wheels at a time and 1 wheel would get power., it was not enough to get the Sequoia up inclines, you would need to lock the center diff. With the torsen both axles always get power, the front up to 53% and the rear up to 71%. ATRAC works side to side on both axles, while the torsen puts it front to back, so it climbs inclines with ease, without the need to lock the center diff.
 
In my experience with this system, on snow and ice unlocked with the torsen working, ATRAC brakes spinning wheels and also cuts power when needed, and keeps the truck in full control. In sand or mud it is better to lock the center diff, this way power is split 50/50, and ATRAC only brakes the spinning wheel, but does not cut power, so it keeps you moving.

#2155 of 2487 Re: RAV4 .vs. Subaru AWD [wwest] by 2toyotas

Jan 16, 2008 (10:03 pm)

Replying to: wwest (Jan 16, 2008 12:19 pm)
Wwest you are right on. My point was if you are going down a highway at 50 mph you wouldn't want ALSD on you would want the default TRAC on. What I meant by TRAC for stability was ALSD does not really cut power, so if you were driving along in ALSD mode and hit ice on one rear tire your back end could slide out, but in default mode TRAC, it would also cut power to keep you straight, hence stability.

#2156 of 2487 Re: RAV4 .vs. Subaru AWD [2toyotas] by hdfatboy

Jan 17, 2008 (6:54 am)

Replying to: 2toyotas (Jan 16, 2008 9:28 pm)
Very helpful summary. Thank you for the timeline info.
 
Just to summarize...the Open to Torsen conversion for the center diff of these models took place in the following years:
 
4Runner - 2003
Sequoia - 2005
LC/LX470 - 2008
 
Is there any other Toyota made 4wd vehicle with a torsen ctr diff?
 
You also shared that the Sequoia and LC/LX changed transfer cases in 2008. The Sequoia from VF4AM to a JF3A. The LC/LX from an HF2A to JF2A.
 
Do you know what the primary difference is between the previous transfer case and the Sequoia's new JF3A? Also do you know what the difference is between the JF2A and the JF3A? Is the primary difference in the transfer cases between the LC/LX and the Sequoia the new "Hill Start Control" and the new "Crawl Control" which are in the LX/LC but not in the Sequoia?

#2157 of 2487 Re: 2008 Highlander, what type of 4WD/AWD system ? [josephd05] by nedzel

Jan 18, 2008 (8:50 am)

Replying to: josephd05 (Jan 16, 2008 2:48 pm)
The 2008 Highlander will do fine on trips to the mall in the snow. I always advise snow tires (which I have on my 2003 4WD 4Runner), since AWD/4WD systems help you go but don't help you stop. Whether or not you get stuck in the snow is all up to you -- don't drive in snow that is deeper than the ground clearance, use some caution, brake and steer gently and you'll be fine. I never got my 1987 Acura Integra stuck in the snow and it was far less capable than an AWD Highlander.
 
The 2008 Highlander is significantly larger and heavier than the previous version, so don't expect to get significantly better mileage than your V6 4Runner.

#2158 of 2487 Guess what... by wwest

Feb 05, 2008 (4:24 pm)

NO torsen in the 4runner after 2003, apparently one year only...!
 
Cannot find any documentation that the torsen was used after 2003 but lots of stuff indicating TRAC was used in its place. Same for the Lexus GX & LX series.
 
Strange, very.
 
Lot of component pictures/diagrams/breakouts of the VF4AM transfer across the years and models but only the 2003 4runner shows a torsen.

#2159 of 2487 Re: Guess what... [wwest] by nedzel

Feb 06, 2008 (8:35 am)

Replying to: wwest (Feb 05, 2008 4:24 pm)
WWest: that is not correct. Go to: http://www.toyota.com/4runner/specs.html
 
Look down at drivetrain: "Multi-Mode 4-wheel drive with Torsen® [1] limited-slip center differential with locking feature" for the V6 and "Full-time 4-wheel drive with Torsen® [1] limited-slip center differential with locking feature"
 
The 4Runner drivetrain hasn't changed since 2003.

#2160 of 2487 Re: Guess what... [nedzel] by wwest

Feb 06, 2008 (10:05 am)

Replying to: nedzel (Feb 06, 2008 8:35 am)
Yes, I know what all the advertising says, hardcopy and on the internet.
 
Clearly, I may be wrong but the information at techinfo.toyota.com is pretty detailed, detailed well enough that a good mechanic could use it to overhaul the transfer system.
 
The word "torsen" is not used beyond 2003 in any of the documentation and I have no idea why that would be unless it isn't used or there is some legality involved.
 
Additionally if you read the document ion for traction control it appears that a torsen diff'l would be of no use since the TRAC system would quickly brake any wheel (and dethrottle the engine simultaneously) that exhibits spin or slip.
 
As somewhat of a parallel, I bought a 2001 AWD RX300 because it had HID VSC/TRAC and a viscous clutch across the center diff'l to provide torque to the rear driveline if front slippage occurred.
 
I quickly discovered that the VC was probably useless since the TRAC system activated at the first sign, seemingly the very instant, wheelspin developed.
 
Apparently Lexus discovered the same thing as the VC was discontinued for the RX330 series as was announced in NCF, New Car Features for the new 2004 RX330.
 
But guess what....??
 
Lexus continued to advertise, hardcopy sales brochures, on the internet, and in various PR pieces, that the RX330 had a VC, Viscous Clutch when the shop/repair manual indicated otherwise.
 
Lexus finally admitted, in writing (email), that the RX330 did not use a VC and apologized for the mis-information.
 
And now here I am arguing with Lexus as to whether or not the new(er) RX350 uses the VC. The advertising says yes but the shop/repair manuals say not and the TRAC use indicates it might be useless even if it is installed.
 
Sorta of like the issue of a torsen with TRAC in the 4runner.

#2161 of 2487 Re: Guess what... [nedzel] by wwest

Feb 06, 2008 (10:11 am)

Replying to: nedzel (Feb 06, 2008 8:35 am)
Read the material, however sparse, on TC, Traction Control, on the provided link.
 
If you have a torsen diff'l in the 4runner wouldn't you need to disable TC in order to put it to use...??

Messages Page 217 of 250

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