AUTO LSD (or Not) for added traction in 2WD?

Maybe my logic is wrong i presumed that there was still "braking" involved even with the e-brake lol...

What i was thinking is that putting the e-brake on is like using a "rear diff lock" since a locked rear diff forces the two wheels to spin at the same speed, engaging the e-brake enough for the engine to over come the brakes so essentially both wheels are spinning at the same speed, one cant slip and spin faster.

I could be totally wrong

 

Sort of a poor man's limited slip? By reducing wheel spin, that lost torque would be shared partly with the traction tire.

However, AUTO LSD doesn't apply brakes to the traction tire only the spinning tire.

 

Not even with ATRAC. By the nature of how a differential works, there is no way you can brake one wheel and transfer anything close to 100% of the available torque to either wheel. There will always be 50% of torque being applied to the braked wheel, even if it is completely stopped. There is no way around it, that is how the system is able to function. An open differential always applies the same amount of torque to both wheels. The amount of torque is determined by the wheel with the least amount of traction. If one wheel breaks traction at 100 ft/lbs, then there will be only 100 ft/lbs being applied to the stopped wheel. It doesn't matter if it is stopped by the static friction with the brake pads, or the ground. What ATRAC type systems do is increase the total available torque by reversing which wheel is determining the available torque. Hopefully past the threshold necessary to move the vehicle.

 

I have tested the auto LSD myself a few times when I got the truck. 1 tire on asphalt, the other in the rock/sand/dust (side of the roads in my small town).

With full throttle applied, the wheel on asphalt will spin and make noise (screech) when going from a dead stop.

I think it sums it up for me...

It works.

 

Yes i realize that, but i mean ca'mon its better than having nothing at all

 

For sure!

 

On a mechanical LSD, there is very little clutch engagement, as the "breakaway" torque setting is very low. Therefor you typically need some traction at both wheels for it to transfer torque. By lightly applying the parking brake, the clutch packs start to grab, limiting the torque difference between the two wheels. Theoretically allowing an LSD to transfer power, even when only one wheel has traction.
ALSD only requires a wheelspeed difference, since it does no use torque biasing, instead it uses wheelspeed referencing / matching algorithms, and generates it's own torque transfer throught thebraking system.

More effective than a mech LSD, but comparing anything but a locker to a locker is apples to oranges. I should mention ALSD will not spin you out on ice as easily as a locker, due it being a mechanically open diff.
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I think the 35 MPH "cutout" is simply because above 35 mph, you generally do not want to be spinning both wheels. This causes the back end to step out pretty fast on snow and ice.

It will harness 50%, same as ATRAC, it just requires more wheel rpm to make it happen. (Basically it just allows smoother operation)

 

On a mechanical LSD, there is very little clutch engagement, as the "breakaway" torque setting is very low. Therefor you typically need some traction at both wheels for it to transfer torque. By lightly applying the parking brake, the clutch packs start to grab, limiting the torque difference between the two wheels. Theoretically allowing an LSD to transfer power, even when only one wheel has traction.
ALSD only requires a wheelspeed difference, since it does no use torque biasing, instead it uses wheelspeed referencing / matching algorithms, and generates it's own torque transfer throught thebraking system.

More effective than a mech LSD, but comparing anything but a locker to a locker is apples to oranges. I should mention ALSD will not spin you out on ice as easily as a locker, due it being a mechanically open diff.
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I think the 35 MPH "cutout" is simply because above 35 mph, you generally do not want to be spinning both wheels. This causes the back end to step out pretty fast on snow and ice.

It will harness 50%, same as ATRAC, it just requires more wheel rpm to make it happen. (Basically it just allows smoother operation)

 

generally i fully agree, but i personally like to do doughnuts and slide around corners, so i wish the cut off did not exist

 

I tow a 16' Carolina Skiff around the state of Florida and the Auto LSD feature was one of the reasons I bought an '09 5 lug in October 2008. My previous vehicles have been Fords with the 3.55 limited slip rear ends and I am familiar with their operation in both towing and 2WD off road situations.

The Auto LSD works as advertised. I have pulled my boat up the sandy side of a canal using the Auto LSD. It has been used on a slippery, weed slimed steep ramp and pulled right up when other vehicles were having to be helped with a winch pulling them from the front.
The owners manual makes it clear that the Auto LSD is not intended for continuous off-road use but, rather, is designed to get you out of place without adequate traction to where normal traction is available.

As a side note I drove out of a wet ditch using just the default traction control and the power was cut substantially. I just held my foot down and the Taco drove right out. When I have used the Auto LSD there has been much more power available and it must be controlled with the left foot. If I find myself in a similar situation again I will engage the Auto LSD before driving out but it is nice to know the Tacoma gets out of a hole without pushing any buttons, too.

 

I tried this going up my drive way because i know its usally somewhat muddy and slippery as i am going up.

I made a little diagram lol, but yeah i put just a tad more gas than i normally to so i can make the wheel spin on purpose...Guess what? NO wheel spin with the parking brake enabled!

 

Just switch to "VSC Off" mode and you're good to go for donuts and burnouts.

 

I made a video to demonstrate how the vehicle performs with TRAC and Auto-LSD. With TRAC active, when wheel slip is detected it will limit the throttle and control the slipping wheel. Auto-LSD mode simply removes this throttle limiting feature all while still controlling the slipping wheel with the brake system.

This test was performed in a very sandy wash out in Jacumba.

http://www.youtube.com/watch?v=zaMd8vTRu4w

David, Please delete and update that blurry graphic in the OP, use this one it is much easier on the eyes.

 

Noo nooo, i dont even have an LSD or ALSD or a Rear Diff Lock.

Im just wondering, atleast i can use the e-brake to "simulate" a Limited Slip or a Rear Diff Lock

 

which is open mode, and a burnout with one wheel spinning is fail. usually snow is still fine, but coming from vehicles with a locker or mech limited slip, its not quite as fun. just wish it was 60 instead of 35.

 

After two Michigan winters I can honestly say I can't tell the difference on my 09 2WD, 5 speed manual trans Regular Cab. Throw 300 lbs of sand in back if you want to go through the snow!

Motoretro

 

Thank you Crom... I made the change! You are a good friend to the Seekers Of Traction Education S.O.T.E.

 

I think this is a very important fact... even locked axles won't do you much good in snow/ice since our beds don't have that much weight on them. You'll just end up with both tires spinning.

If stuck in snow, I always had to put in 4x4 since I refuse to carry sand bags.

 

In Baja, the Mexicans put rocks in the back of their pickups (if they are otherwise empty) to improve traction... VW beetles (the air cooled ones) were fantastic off road becaue the engine was in back, over the drive wheels! The Baja Bug and VW powered dune buggies were a direct result!

 

I have been going to Baja for off road races ever since I bought my prerunner. I have witnessed what a 2wd Tacoma with LSD and a few hundred pounds of weight in the bed is capable of. I have only been stuck ONCE! and that was my first time driving the truck off road (First time driving off road, PERIOD). I've been in deep sandy washes and have not gotten stuck. I always have 4 people and camping gear (2 ice chests full of beer and ice, tents, chairs, etc [sometimes take the quad instead of the coolers]) in the bed and am amazed at where I can go without getting stuck in 2wd.

The last race I went to was in laguna salada. There was a somewhat steep decline we came down and would eventually have to go back up. Later, We saw a group of jeeps and 1 ford ranger go up the incline. A couple of the jeeps made it up in what seemed 2wd, a few stopped midway and must have engaged 4wd, and poor old Ford Ranger has his rear tires spinning like crazy, so engaged 4x4. This made me nervous as we were by ourselves with no locker or 4wd. All I have to say is that I crawled up the incline without the slightest feel of wheel spin... Mechanical LSD and weight in the back of a TOYOTA FTMFW!