Simulated LSD in rear diff?

I was at the dealer and feeling them out on ordering at 2023. I want 2 wheel drive and mentioned it was really 1 wheel drive. i then went thru my spiel that they use smoke and mirrors and by doing something with the brake system and call it LSD. the salesman then said they don't have that anymore and the rear wheels both lock up now.
First I have heard of this, anyone out there know what he is talking about.

 

It's brake based (i.e. cost Toyota nothing to implement with existing ABS hardware). Every Toyota built since 2009 has it. Pretty effective unless you're on a loose surface (sand or snow) and need both wheels spinning while locked.

 

first of all just because one tire will spin by itself at times does not mean its one wheel drive. an open diff is sending the exact same amount of power to both (as in 2) wheels in 2wd.

secondly there hasnt been a mechanical lsd since 2008 and auto lsd is based off the traction control system which does work quite well but isnt consistent at times and stability control and some traction control has to be on to use it.

 

so this salesman is feeding me a load of crap?

 

You are correct and those that say open diffs are one wheel drive are clueless as to what's actually happening and how differentials work. However, one correction, open diffs send equal torque to both wheels, not power. Power sent can be unequal because torque is always equal but speeds do not have to be and power is torque times angular velocity (speed).

 

Yes, it's a salesman, so that's pretty much a given.

 

My 09' was the first year the auto LSD was standard on them. I liked it. There's no clutch packs to wear out which is a plus. You can install an LSD if you'd like a Detroit Truetrac.

 

Where are the flashbacks they all warned us would come?
Buffett

 

You have got simulated LSD and TC in the rear that work pretty good. 100 times better than an open diff.

 

There is some confusing and misleading information in this thread. Here is some detailed information on the traction control modes.

https://www.tacomaworld.com/threads/3rd-gen-traction-control-modes-explained.530695/

 

You're wrong. Both get equal torque but the torque each get is limited to the traction available at the wheel with the least grip (your spinning one) . But the total torque still must be enough to overcome all the static load (friction, rolling resistance, gravity, etc.) to get the vehicle moving because positive torque at the wheel isn't enough, it must be positive net after all the loads keeping the vehicle stationary are overcome. In your case it wasn't.

 

Power is not torque, torque is not power. I've done this song and dance too many times on this forum so search my username with "torque", "differential", etc. to learn.

Facts again for quick reference:

Open differentials output equal torques and unequal speeds. The max torque each wheel will get is limited to the traction available at the lower grip wheel. This limitation is the pitfall of an open diff. It's also this equal torque output characteristic that allows the tractive systems like autoLSD and A-TRAC to be effective.

LSD's can output unequal torques and unequal speeds. This is their function, to bias torque to the wheel with higher traction. Just because both wheels spin it does NOT mean they must be receiving equal torque (sorry intuition). The relationship of torque bias and differential speed depends on the type of LSD and its setup (it gets complicated I admit). As a rule of thumb, the slower spinning wheel receives the higher torque.

A locker outputs unequal torques and equal speeds. This the is king of torque biasing devices and can output up to 100% of the drive torque to one wheel. A locker will always utilize all available traction at both wheels before spinning.

I have pretty deep and specialized knowledge in this area and these facts are proven by physics, test data, and implementation. Intuition will steer you astray.

 

torque yes but i dont wana sound to phansee here. i also call a wheel a rim. i see your other comments down below and looks like your arguing with a lost cause.

 

the torque is equal to the tire with the least amount of traction. one wheel will almost always have less traction than the other so even with same torque applied to both wheels that one with less traction is going to break free. never at any point is there less torque being sent to that other wheel. it simply has enough traction to resist that torque while the other doesn't.

 

Usually I am pretty good with thinking of a different way to describe something so people understand... but I don't know how to say it any different than @ShimStack

There is one known in an (normal) open diff in a steady state condition. Torque on LH driveshaft=RH driveshaft.... doesnt matter if its spinning a wheel, stuck in mud, turning on dry pavement or cruising down the highway.

Once you accept that, everything else falls into place...

(Note, for a locked diff, the angular speed LH = RH, and you know nothing of the relative torque in general)

 

Torque applied to a wheel doesn't mean it has to move. Yes, for torque to exist in the system it must either be reacted by something (traction, friction, drag, etc.) or accelerating something.

With an open diff the torque at EACH (they're equal) is limited to the available traction from the LEAST tractive wheel. Once we hit that limit all excess torque goes to accelerating the drivetrain up to the rev limiter. The wheel with traction is also getting whatever small torque is going to the spinning wheel to overcome drag and accelerate it but it's not enough to over come the static load and get the truck moving.

 

Sounds like someone needs to subscribe to the Engineering Explained YouTube channel... And it ain't @ShimStack

 

How do you know for sure that those tire marks are from a Posi Trac differential?



Hey @op, the little pamphlet at the dealer or even the Toyota website could have proved that salesman wrong in about 2 seconds... Only (some) of the TRD trims get a push button selectable e-locker, but they ALSO have the simulated-brake-actuated-LSD as well, just like the lower trims.

 

Yes, but he probably doesn't know it.