Last post on Aug 21, 2013 at 5:16 PM
You are in the Toyota Sequoia
What is this discussion about?
Toyota Sequoia, Toyota Highlander, Toyota 4Runner, Toyota Land Cruiser, Toyota RAV4, Toyota Tacoma, Truck, SUV
#2116 of 2493 Re: RAV4 .vs. Subaru AWD [kurtamaxxxguy]
Jan 14, 2008 (8:03 am)
It really depends which Toyota 4wd system you are referring to. The new system in the 2008 LC, Sequoia, LX570, 4Runner and LS600h uses a mechanical LSD for the center differential which is not the case in the 4wd systems of Toyota's lower priced vehicles or last year's models.
This newer system does not exist on most of their older models (I think it was on the older 4Runner models). I believe there is still a significant disadvantage that remains in Toyota's A-LSD system.... it does not function above 35mph. This limitation means that for all of these Toyota vehicles with the new 4wd system, when operating above 35 mph, they really only have traction to one wheel on the front end and one on the rear distributed through the mechanical center differential (the rear differential is still open on the new 4wd system). This can make a difference on wet highway ramps and other higher speed situations (above 35mph) where traction at all 4 corners is desirable.
The power is distributed through the new Torsen Center Differential with a range of 30/70 upto 50/50 when operating in full-time 4wd. The other downside to Toyota's A-LSD is that because it is based on using the brakes to distribute torque when there's slippage (below 35mph), it can have a tendency to wear out brake pads sooner than a system that doesn't use brakes to distribute torque (ie, mechanical LSD or lockable LSD). I don't know how much additional wear there is but it must be something vs a non-brake method for distributing torque during slippage.
Toyota's new full-time 4wd design is better (for on-road use) than the old system which had 3 open differentials, but its still not as good as AWD systems used by Audi, Subaru, Dodge, GMC and Cadillac that use a LSD for the center and the rear of their FT 4wd drivetrains.
#2117 of 2493 Re: RAV4 .vs. Subaru AWD [hdfatboy]
Jan 14, 2008 (9:39 am)
"..when operating above 35MPH...."
In normal, non-adverse roadbed, conditions none of these engine/transaxle combinations will produce enough torque to induce wheelspin/slip above 35MPH, so above that speed the number of driven wheels is generally not of matter.
If you have reached 35 MPH and the roadbed is slippery enough that the engine will induce wheelspin/slip and you force it to do so you simply do not belong on the same roads as others with more common sense.
With A-LSD I suspect the manufacturers have an expectation that over time the drivers will adapt to "learned" road conditions and thereby do their own "feathering" of the throttle to avoid wheelspin/slip. That should avoid most uses of the brakes to implement the A-LSD system.
The TC, Traction Control, system in my '92 LS400 works very well as a warning, heads up indication, of roadbed conditions for which I may have been unaware, was unaware, but once I get that warning I typically turn it off and drive a bit more cautiously, as conditions warrant.
#2118 of 2493 Re: RAV4 .vs. Subaru AWD [wwest]
Jan 14, 2008 (10:22 am)
"In normal, non-adverse roadbed, conditions none of these engine/transaxle combinations will produce enough torque to induce wheelspin/slip above 35MPH, so above that speed the number of driven wheels is generally not of matter.
If you have reached 35 MPH and the roadbed is slippery enough that the engine will induce wheelspin/slip and you force it to do so you simply do not belong on the same roads as others with more common sense."
Your view may be reasonable however there have been enough circumstances where I was on a sloping ramp in snowy or wet conditions that I was glad I had a true AWD/FT 4wd system that incorporated a mechanical LSD in both the center and rear differentials. Obviously Toyota engineers felt it offered enough of a benefit to warrant their change over to a mechanical center differential on their newest high-end 4wd models. I just wish they had done the same on the rear differential for the same reason they elected to incorporate it into the center differential.
I would think MB, Audi, Subaru, GMC, Dodge, Cadillac, BMW, Chevy, Land Rover, Porsche designed their AWD/FT 4WD systems with a mechanical LSD in both the center and rear of their drivetrains for a good reason. IMHO that reason being that it delivers a more sure-footed driving experience without the speed limitations and brake wearing downsides of the Toyota electronic approach.
#2119 of 2493 Re: RAV4 .vs. Subaru AWD [hdfatboy]
Jan 14, 2008 (2:40 pm)
Are you really sure that all those you named, AWD/FT 4WD systems, truly have a rear mechanical LSD..?? When the primary drive is not at the front a rear mechanical LSD vs a brake implemented LSD might make little difference in actuallity, all conditions.
#2121 of 2493 Re: 4wd/AWD with limited slip rear diffs [hdfatboy]
Jan 14, 2008 (9:02 pm)
"..provides a limited slip rear differential"
Uisng a viscous clutch, a spring pre-load clutch set, or....
#2122 of 2493 Re: RAV4 .vs. Subaru AWD [hdfatboy]
Jan 14, 2008 (9:59 pm)
You should really know more about Toyotas 4WD Systems before commenting. First, the Torsen Center Differential has been in the 4Runner since 2003, and in the Sequoia since 2005. Second ALSD only operates in 2WD, and is engaged by pressing a button. All other times TRAC is on, and works at any speed. TRAC will brake the slipping wheel and cut engine power for stability, which is what you would want above 35 mph. ALSD will brake the slipping wheel to give equal power to each wheel. When these vehicles are in 4WD ATRAC operates at all speeds on both axles. When the center diff is unlocked the Torsen will split power 40 front and 60 rear in normal driving, and up to 53% of power can go to the front, and 71% can go to the rear. ATRAC will brake spinning wheels and cut engine power for stability. When the Center Diff is locked power is split 50/50 and ATRAC will just brake spinning wheels, it does not cut engine power. When LOW range is engaged ATRAC does not cut engine power, and brakes wheels to keep driveability, instead of stability. This is on both front and rear axles, and is said to be equal to a vehicle with the center and rear diffs locked. A Sequoia, 4Runner, or Land Cruiser/LX570 will go farther without getting stuck than any Cadillac,Denali,Audi, or Subaru.
Jan 15, 2008 (7:37 am)
To recap, 2toyotas, how does the RAV4s' 4WD system work?
Is it similar to the 4runner?
#2124 of 2493 Re: RAV4 .vs. Subaru AWD [hdfatboy]
Jan 15, 2008 (8:27 am)
"The new system in the 2008 LC, Sequoia, LX570, 4Runner and LS600h uses a mechanical LSD for the center differential which is not the case in the 4wd systems of Toyota's lower priced vehicles or last year's models.
This newer system does not exist on most of their older models (I think it was on the older 4Runner models)."
All of the 4th generation 4Runners (from 2003 on) have a lockable Torsen center differential. The same is true of the GX470. I believe that the previous generation LandCruiser and LX470 also used the same lockable Torsen center diff.
#2125 of 2493 Re: rav4 [kurtamaxxxguy]
Jan 15, 2008 (8:30 am)
No, it is NOT similar at all to the 4Runner. The 4Runner has a lockable Torsen center differential and a low-range. The RAV4 is a FWD vehicle until the rears slip...