I have a question about the 2012 limited's 4WD system.

It's a full-time 4WD system. Does that mean when the selector knob is at H4F that it operates like an AWD system where it may not be a 50/50 split of power between the front and rear axles, where 80-90% of the power may be sent to the rear axle and more is sent to the front only when needed?

The owner's manual says that H4F (center differential unlocked) should be used for driving on "dry hard surface roads." I would hope that in H4F it would be good in light snow and ice too. Isn't that the benefit of having full-time 4WD; you don't have to worry about shifting it in and out of 4WD because of patchy snow and ice on an otherwise dry asphalt road?

It sounds like when it's put into H4L (center differential locked), the power is now split 50/50 between the front and rear axles, and it's the most stable, even more than H4F.

Is having it in H4F a very good system for snow and ice covered roads too?

The 5th Gen Limited does indeed have a full-time 4WD, often called AWD system because the torque split is variable. The standard split is 40/60 front/rear I believe and can be commanded up to 60/40. Its a mechanical 4WD using a Torsen 3rd generation center diff which is why the torque split is what it is (Torsen actually lists the T-3 as a 35/65 or 65/35 split). Other AWD systems can decouple the second pair of drive wheels and favor a more traditional FWD or RWD until traction loss is detected; not so with the 4runner.

The full time 4WD is indeed great for slick roads because the system always tries to maintain traction, albeit with interference from the brakes and engine throttling. A traditional 4x4 system, or with a fully locked center diff, actually must LOSE traction on one or more wheels to dissipate driveline differences. This is great offroad or in a straight line but a little less than desirable when negotiating slick corners. So to summarize, 4HI unlocked is a variable biased torque system using a (lockable) Torsen center diff to send the majority of power (not all) either front or rear. Its great onroad and in slick conditions, especially with the electronic aids deactivated. 4HI locked should be used for mud, when stuck, or offroad as speeds are generally slower and traction losses are not likely to result in a skid.

Thanks for the excellent explanation. Now, when we do get some snow out here, I'll leave it in 4HF, unless it's of the blizzard variety. Then, I'll use 4HL in the deep snow since I'll be driving much slower.

**especially with the electronic aids deactivated**

Can you explain why this is better and link to how to do it?

Just push the VSC Off button.

Sorry to pull up an old thread but I'm having a hard time finding some answers

My dad has a 2012 Four Runner, for a while I've been hearing a "droning" noise in it. Last night I put brakes on it for him and started looking around for the possible culprit. I couldn't find a wheel bearing that felt rough or made noise. U-joints seem tight. I noticed the front hubs were locked when I spun the a wheel....but my F150 does the same thing, it uses vacuum to unlock the front hubs once the motor is started. I started the motor on the Toyota and they remained locked, is this normal? I'm wondering (or hoping) there is a switch that is bad and what I am hearing is all the 4wd parts turning.

I must say I was less than pleased to see the rear diff is designed like the 9" and no cover, I assume the axle shafts have to be pulled in order to get the differential out to look for wear? Unfortunately the droning does sound like it could be differential noise, although it should have gotten worse by now.

Thanks for the help

If you dad has a Limited it's full-time AWD. front hubs will always be "locked".

When I switched to Mobil 1 synthetic dif oil mine got quieter.

Sounds like the noise is somewhat normal, in which case since by dad is hard of hearing and can't hear it and I don't drive it often I don't see any reason to take the rear end apart

What's your Dad's mileage?

year old thread but still applies no matter the age of the vehicle I suppose. The dealer I just bought mine (used) from said that the difference in tread from putting new tires on was less than 2/32nds and not to worry. Reading all about it now has me worried and i might just put new tires on with a leveling kit and call it peae of mind since it hasnt been over 300 miles since the new ones were put on there.

They put new tires on with different tread depths? or the tires are worn and the tread depth is different?

They put two new tires on the rear, the other ones weren’t new ok but pretty close to it. All the same tire just measured less than a 2/32nds difference which they said was fine.


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Make them replace all the tires or return the car.

I absolutely wouldn't buy a car from a dealer that's too cheap to replace all four tires, especially on an "AWD" car.

Assume the other tires don't have other issues 1/16th of an inch - isn't a big deal. Air pressure variation is likely to make just as much of a diameter change. If it really bothers you I assume you can still have tires shaved or feel free to replace them but the 4runner won't care.

back of the napkin - for a 31" tire and a 31.125" tires its 650.58revs/mile vs 647.97revs/mile - your differential is not going to care.

Also was not clear which two tires would changed (really makes no difference other than the front or rear differentials eat the variation or the center differential in the transfer case eats it.