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Hello,

I bought a used 2013 HH Limited and a mechanic at the oil and lube joint informed me that this is not a true All-Wheel-Drive vehicle because of the hybrid engine and how it operates in conjunction with the gas engine. Does anyone understand the mechanics behind the 2nd gen Hybrid's AWD technology and can explain this to me? If he's just full of it or not, I'd like to know. I count on true AWD capabilities in winter to drive my family around in this car. Thank you!
 

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2008 Highlander Base
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I know this has been discussed in the past, but I don't recall which thread. I'd recommend using Google to search the forums, and use "toyotanation.com" in the search string to return relevant results. Still, just offering this up, here's a thread from the 1st Gen Highlander forum that may offer a bit of insight:

 

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Highlander Limited
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In short the front wheels get power from the gas engine and the rear wheels have electric motors that turn them. As long as you have good tires the hybrid is just as good as any other awd/4wd car out there. It's actually better than the all gas version since both a front and rear wheel can be powered at once. The gas version uses open differentials so of the 4 wheels only one gets power. Now the traction control system helps mitigate that, but it still isn't a very good system.
 

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Actually.. AWD is a very vague term and all it really means that each wheel "could" receive power from the engine.. under the right circumstances. Different manufacturers employ different tricks, both mechanical and software driven but none have true AWD.. if, you define AWD as each wheel being powered independently from each other.
 

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08 Toyota Camry 2AZ-FE R9K Tuned
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Actually.. AWD is a very vague term and all it really means that each wheel "could" receive power from the engine.. under the right circumstances. Different manufacturers employ different tricks, both mechanical and software driven but none have true AWD.. if, you define AWD as each wheel being powered independently from each other.
The definition of AWD is just as confusing as 4WD or All Time 4WD. ?‍♀
 

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Up to 2013 the HL is 4WD, there is not electric/electrical rear axle coupler as in pretty much all others made. Its mechanic and may have viscous intermediate transfer case of some sort to correct for wheel speed and shaft speed combo difference however the engineers worked it out. Bottom line is we won't be replacing AWD electrically controlled couplers as Kia/Hyundai owner have to, even still they fail around 40-50,000km of use.

This was a key point in me selecting this earlier years design buying it two years ago. The front and rear are always working on these. HYBRID obviously different due to the motors electrically driven which would be better than the outer type of coupler I mentioned which fail.
 

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There are no viscous couplings in these of any kind.
Up to 2013 the HL is 4WD, there is not electric/electrical rear axle coupler as in pretty much all others made. Its mechanic and may have viscous intermediate transfer case of some sort to correct for wheel speed and shaft speed combo difference however the engineers worked it out. Bottom line is we won't be replacing AWD electrically controlled couplers as Kia/Hyundai owner have to, even still they fail around 40-50,000km of use.

This was a key point in me selecting this earlier years design buying it two years ago. The front and rear are always working on these. HYBRID obviously different due to the motors electrically driven which would be better than the outer type of coupler I mentioned which fail.
Up to 2013 the HL is 4WD, there is not electric/electrical rear axle coupler as in pretty much all others made. Its mechanic and may have viscous intermediate transfer case of some sort to correct for wheel speed and shaft speed combo difference however the engineers worked it out. Bottom line is we won't be replacing AWD electrically controlled couplers as Kia/Hyundai owner have to, even still they fail around 40-50,000km of use.

This was a key point in me selecting this earlier years design buying it two years ago. The front and rear are always working on these. HYBRID obviously different due to the motors electrically driven which would be better than the outer type of coupler I mentioned which fail.
There is no viscous couplings of any kind in these. They use 3 differentials in the system. One in the rear, one acting like a transfer case would and one for the front. They are always mechanically connected which is nice. The downside is that because they use 3 open differentials and no type of lock the awd/4wd is not very good. At any time 100 percent of power can go to only one wheel and that wheel would be the one with the least traction. The traction control uses the brakes to mitigate this, but it's still not a very good system. The type you talk about with the rear electromagnetic couplers is much better for suburban day to day use. I had 2 Rav4s that used them and a Kia Sorento and none of them ever had any issues. I myself prefer something with a lockable transfer case. I have been eyeballing the newer 4runners.
 

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I still prefer this design. Its maintenance free without true fail points. I have a 2015 Sorento and the coupler was already shot at 48k km when we bought it from a Kia dealer. Lots of failure pop up on the kia forum which I am also on. They don't last as implement for suburban driving as you imply and something to be aware of purchase used or new. They will go (fail). This is a Gen 2 build the 08 and 09 I expect were different.

Locking diffs are rare and only Nissan that I know put them into their rear pathfinders back in he day. Jeep Rubicon also had a system front and rear but maintenance intensive with fluid changes often for them.

I only new about the middle and not at the rear (unless the one within the diff is what you're implying)

Anyway so far I am fine with its system because its all mechanical and working for me. Those other AWD coupler also require a very smart software package including some smart ABS intervention.
 

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This system is a decent one for sure. I think it's good for a vehicle of this size, but it would be nice to have a locking center diff so both front and rear would get guaranteed power. I think your Sorento was a dud. Mine is at 96k miles with no issues other than a door lock assembly. I think the electromagnetic couplers go bad due to over using them. They are definitely not as tough.
 

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This system is a decent one for sure. I think it's good for a vehicle of this size, but it would be nice to have a locking center diff so both front and rear would get guaranteed power. I think your Sorento was a dud. Mine is at 96k miles with no issues other than a door lock assembly. I think the electromagnetic couplers go bad due to over using them. They are definitely not as tough.
Yes, the electromagnetic couples as in Kia/Hyundai cannot be turned off. They are active pushing when pulling out of turns etc in the summer as well when the front has 100% traction. The AWD button only forces it on from the moment you start moving and not waiting for a wheel to slip. Fine for getting in/out of driveways, parking spots where low speed is in place since they disengage as the speed hits around 25 MPH or such as on a regular road/highway only the front are really working. Some people pull the AWD fuse in the summer to kill this action extending life.

I have had various true 4x4 vehicle w/transfer cases but non had locking diff. An Eaton or other lockers could be added, (Jeep 2002 Grand Cherokee, GMC S10 4x4, 1991 Explorer 4x4) as well as many AWD's over the decades. They are all much better than a FWD vehicle and I drive with confidence in them all. Tires are key in trying environments as the original Michelins which came on the HL are useless in the snow or slushy roads, I have snow tires now on the HL.
 

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Pretty much disregard most of the posts above describing various NON HYBRID AWD systems.
What you have is simple.
You have hybrid drive in the front, called PSD, Power Split Device. 2 electric motors coupled with epicyclic gear set. Very unique to Toyota hybrids only.
That is what normally drives the vehicle.
What you have in the rear is smaller version of the same PSD.
All electric operation with same gear set.
THERE IS NO MECHANICAL CONNECTION BETWEEN THE TWO.
When front wheels slip, rear wheels kick in and you have AWD. Rear axle power input is supplemental and is turned off as soon as front slipping condition is gone.
Also, if you REALLY stab the car and there is high power demand from power train, rear PSD will also kick in, for short time.
Reverse is electric only and front.
Plenty of Youtube videos Highlander Hybrid in snow or in sand. Have at it.
 

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No, just when I think of anything "locking" I think of 4WD. When I think of AWD, well... I don't know what I am thinking other than all wheels spinning.
Rear drive based = 4wd and front wheel based = awd. I also consider off road capable as 4wd and not off road capable awd. These days the lines are so blurred I just don't care LOL.
 

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Rear drive based = 4wd and front wheel based = awd. I also consider off road capable as 4wd and not off road capable awd. These days the lines are so blurred I just don't care LOL.
Though it's those minor difference that matter...
 

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AWD, 4WD, ... just marketing terms for fools.

Years ago, I didn't care for the hybrid AWD in snow, especially without snow tires. What happens to the batteries when they are cold? What happens to the rear electric motor when battery charge state is low? How much 'push' can you expect from the rear wheels when really needed? I guess that Toyota has improved the 'programming' of their Hybrids over the years because I find that the newer ones are at least 'tolerable'.
And, I do recommend all-weather or snow tires when weather required vs. the krappy no-season sh!t that all cars come with now for the brainwashed by marketing masses. I've driven both hybrid and non-hybrid Highlanders in blizzard conditions. And, when living up north, I would not have even considered a hybrid with pseudo-AWD. But, it is a true AWD when it is working up until the point of it not working. I'd just take a prop-shaft equipped Highlander over a non-propshaft equipped Highlander, unless the MPG is a must.

The MPG for the hybrid is excellent for the vehicle. So, I am not a hybrid hater. I just don't expect it to work as well as a mechanically linked All/four/almost wheel drive system. I say almost-wheel-drive, on the non-hybrids, because of the open differentials at the mercy of the traction control system, along with torque limitations of the electro-magnetic clutch packs, and speed limitations that shut off or limit the 'push' from the rear wheels as speed increases on pretty much all marketed as AWD Toyotas(Rav4 Venza Sienna and all non 2nd Gen Highlanders). The 2nd gen 2008-13 Highlander non-hybrid used a tire scrubbing locked transfer case(really a power take off) and was pretty capable for a vehicle without a low range.

So, is the 2013 a 2nd or 3rd gen and is the OP in the right forum? And, with that user name, one in the Rocky Mountains, OP's user name, should consider a dedicated set of quality snow tires for winter usage.... Michelin, Bridgestone, Nokian...

Enjoy the hybrid and don't expect it to crawl over monsta' rocks, drive thru mud pits or tank traps, or plow thru 48" of snow, and you should be fine.
 

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No, just when I think of anything "locking" I think of 4WD. When I think of AWD, well... I don't know what I am thinking other than all wheels spinning.
That's why I always use the term 4x4 instead of 4WD because it's more clear, at least to me.
 
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