Question about Auto Limited Slip

This is my first Tundra and first post. The window sticker reads, "4WDemand Part-Time 4WD w/Elec Controlled Transfer Case and Auto Limited Slip Diff."

Reading through the owners manual last night I stumbled on some wording that Auto Lim Slip is only for 2WD. Do they mean 2WD Tundra 'models' or 2WD 'drive mode'? Is that even correct?

Do I have to be in 2WD, or switch traction control off? Does TC have to be on? Do these matter for Auto Lim Slip Diff to work?

As an aside, my Ridgeline was full time AWD with specific modes for snow, sand, mud and normal. My particular Tundra does not have the TRD offroad package although I know the TRD trucks have these modes plus others. (My Tundra has the auto leveling pneumatic rear suspension).

Anecdotally, the way it worked on my Ridgeline, when I was stuck in the mud, if you feathered the gas it wouldn't move unless you had enough speed difference between the spinning wheel and the one not turning, but if you punched the gas it would see the difference and apply brake to the spinning wheel causing both of them to turn and move smartly out of the stuck predicament.

For the Tundra I would have thought it should be enough to just be in 4WD, and maybe turn TC off, but hopefully not have to go into 2WD for the Auto Lim Slip to work.

 

Hello.

Auto limited slip differential in tundras is nothing more than computer applying brake to the spinning wheel to get the non-spinning wheel going.

 

ALSD works similar to your ridgeline’s system and as @EmergencyMaximum noted - it’s the computer applying the brakes to limited wheel speed. Though, there are some things to note about using it

ALSD only functions in 2wd (on both 2wd and 4wd vehicles), and only at lower wheel speed. If you are in muddy or slick conditions and feed it some pedal, it will only cut power and shut down your attempt. Instead, feed it steady throttle input to raise the RPMs to 1500-1800 and let it do it’s thing. It takes a second to “read” the tire traction scenario, but will bias enough power to move the vehicle so long as one whee has enough traction to do so. You’ll hear the ABS clicking and clunking which is a good sign. Hold it steady and pint it where you want it to go. I’ve crawled through ditches flexing out the suspension using the feature with success.

In 4wd, Toyota no longer calls it ALSD, but rather ATRAC, which is the same thing just in 4wd. The torque biasing program is different from 2wd to 4wd (you don’t want the front brakes applying in 2wd, for example) so they just call it something differently entirely.

ATRAC is also great for loose terrain management where wheel speed is kept very low. In mud or other terrain where higher wheel speed is desired, disable the ATRAC and/or traction control and let it eat. That usually requires a few push/hold button procedures.

There are some very big differences between the Ridgeline AWD and the tundras selectable 4wd. AWD on the ridgeline is a part time system - it runs in 2wd then automatically selects AWD if it senses wheel slip. There is also a differential between the front and rear axles in the transfer case; this is necessary for operating 4wd on dry pavement (making it AWD instead of 4wd) but just like a standard open differential in your axle, power flows to the path of least resistance and you can get one wheel spinning while the others r standing still. That’s why it’s necessary to use the braking system to limit wheelspin.

The tundras 4wd system locks the front and rear driveshafts together pushing a 50/50 torque split front to rear. The brakes only need to differentiate side to side on one axle rather than try to manage torque for all four wheels, if that makes sense. This system is generally more robust and effective in off pavement or low traction situations, but is not suitable for high traction like pavement as all four wheels turn at different speeds in a corner.

To confuse the mix even more, older Gen sequoias have all drive modes - 2wd/AWD/4wd/4Lo/4LoAWD. They use a true helical gear type limited slip differential in the transfer case to bias torque front to rear, keeping all the torque from being sent to one wheel, while differentiating front to rear so it can be driven on pavement like the ridgeline. But push a button and it locks the front and rear axles together like your tundra for true 4wd.

Just trying to help muddy the waters a little for u…

 

I really appreciate the thorough, detailed explanation Blenton (and E-Max). Very helpful! I'm not sure what is meant by "requires a few push/hold button procedures," ..of the traction control button? On mine, I don't see anything specifially called out as ATRAC, there is console button depicting a squigly tire tracks and an indicator of the same in the dash display when you turn it off, otherwise for all intents it appears to be 'on' all the time.

I don't seek out 4WD trails, and need 4WD only infrequently, but occasionally am glad to have it, or AWD. The last time was in late Autumn, I was in the San Juans Forest taking a shortcut through a Reservation land around Pagosa Springs Colorado on my way to Taos N.M. It had been raining for days and the high mountain pass had turned to slick and mud. In the Ridgeline, I hit it with momentum, sawing back and forth at the wheel to keep it centered but the slope was winning and my momentum stalled out. I had to back my way down staying precisely centered on top of the crown because just a tiny slip meant a worse predicament of a muddy ditch on either edge with darkness approaching and no help, no cell service, so I was very careful, backing for 1/4-3/8 mile to reach a spot where I could turn around. Even so, at one point only an eyelash away from stuck, the rear wheels teetering at the drop into the ditch, but that day the Honda AWD had just enough to pull me out, whew! As you said, the anti-lock braking system could be heard limiting the slip. I have had other vehicles in the past with true part time 4WD systems, a couple Silverados, a Titan, an F150, a couple Tacomas, some manual transmissions, several had locking differentials, but seldom used or truly needed these features, but when you need it, you NEED it. The expression was, "4WD doesn't mean you won't get stuck. It just means that when you DO get stuck, it will be in a worse place!"

Interesting about the Sequoia 4WD/AWD. One of my Silverados had something called Autotrac. It sensed slippage and engaged the part time 4WD but this was a crude kludge. The Ridgelines were very good to me and all I need for towing my 2300 lb camping trailer but after owning 2 of them for the last 8 1/2 years I wanted to try something different. My only two annoyances with it were the lack of trailer brake controller and headlamps excessively high/bright when towing, not really sagging more than a fraction but just enough to annoy oncoming drivers. The Tundra will also permit me to rent some equipment, small backhoe, skid steer that the Ridgeline couldn't. Really enjoying the new Tundra so far.

But again, great explanations above about the transfer case differentials, torque splits, thanks!

 

You should be able to find this info in the manual, but basically push the traction control button once (the squiggly line button) to activate the ALSD in 2wd; push and hold for approximately 5 seconds until more lights on the dash illuminate to partially disable traction control but still have ALSD (more wheel speed but it will still shut you down if you get rowdy); push and hold for an additional 3-5 seconds to disable traction control completely so you can get sideways in 2wd without the Nannie’s.

In 4wd, I think there’s only a single push, or push and hold once to disable traction control.

Glad you are enjoying the tundra. Sounds like you have a background in traditional 4wd, which is great. I’ve owned a few of those vehicles myself and know what you mean saying the auto track was a crude kludge. I rarely used 4wdAuto in my GM’s because of broken diffs, ujoints, and tcase chains and parts. After purchasing a 2nd Gen sequoia as the family truckster, I LOVE the torsen type center diff and wish it came on every Toyota truck.

 

So here is an update; The traction control button on the center console is labeled, "Traction Off." Pressing it causes a message on the instrument panel display "Traction Control Turned Off." Press again and hold displays an additional message 'VSC Turned OFF, Pre-Collision Brake System Unavailable." The default condition therefore is Traction ON. This works the same whether in 2WD or 4WD.

 

Correct - traction control defaults to 'On' and resets back to 'On' every time you turn the vehicle off. Push and hold the TC button a second time and see what lights up on the dash.

 

If I push and hold the TC button a second time, it just reverts back to the default traction-on condition with nothing lighted up, no ALSD indication.

 

Interesting... when I went hoonin' around in a 3rd gen on a test drive, I'm pretty sure that's how I was able to turn off all the nannies and spin donuts in the parking lot (snowy, icy parking lot...). What does your owner's manual say about it?

 

You need to just press and hold once until you see all the messages pop up. It takes around 5 seconds.

If you just click it, you get a traction control disabled message, If you click it, release it and then press and hold, you will turn it back on.

 

If I momentarily press the traction off button, it displays traction control off message. If I press and hold for 5 seconds or longer, it gives the traction control off message, but then also another message saying VSC is also off, an icon for each on the screen. I will look into the owners manual for explanations soon. The long press doesn't work after attaining a certain speed; have to slow down or stop to turn VSC off.

 

That’s correct. You have to be stopped in order to disable it or change modes. Now press and hold a second time and see what happens.

 

You can be moving to turn traction control off, with just a momentary press of the traction-off button. But to turn off traction control, VSC and the radar you have to be stopped or moving very slowly, with a long press. A second long press just reverts back to the default traction-on. That's how it's working on mine anyway.

 

Correct. You need to be stopped or moving very slowly like you said. They want you to disable it before hand and not on the fly.