Quick question regarding LSD

JeffMerr

JeffMerr

New member
I was researching Detroit TrueTrac but recently noticed my 2006 Sport Edition has a button which says "AUTO LSD" that I can select to engage. I'm pretty green to this stuff, is the AUTO LSD which comes stock on the 4runner basically the same thing as a rear Detroit TrueTrac system? Meaning they do the same function. Thanks.
 
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So according to that thread, the stock AUTO LSD will engage the other rear wheel? So I will have both rear wheels working together when trying to get up a slippery hill for example? I have 2WD btw. It seems like the main difference is that traction control regulates throttle.
 
I had the same question when I got my 4Runner. That thread should be stickied or added to the "Pre-Purchase Info, Modifications, Write-Ups, Quick Links, and FAQ's " thread.
 
Sooo what did you learn? I did a search but not much came up. Still trying to find out if a Detroit truetrac would be a cost effective advantage over the stock auto lsd.
 
The way open differentials work is that power goes to the wheel with the least resistance, so if one wheel is in the air spinning the other wheel won't move.

Our 4runners come with open differentials (if you have 4WD, the center is limited slip), and the traction control system uses the brakes to control a wheel that's spinning too fast and send power to the wheel with traction. Traction control is always on unless you disable it, so you get most of the benefits of the system all the time.

Auto LSD seems to change the programming to make the limited slip feature more aggressive and reduce the throttle cut feature. Here's my impression of how it works:

If you are on a slippery surface (like snow) in normal mode and you hit the gas to accelerate hard, it will detect that the drive wheels are slipping and cut the throttle (it's drive by wire, so it can do that). It will also use the brakes to distribute power to the drive wheels with traction as well as it can. The result will be that you will slowly accelerate with minimal slipping, no matter how hard you press the gas.

If you are on the same surface and you put it in Auto LSD mode, it won't cut the throttle (as much?) if the drive wheels are slipping, it will just try to get them to turn at the same speed. The result will be that you accelerate slowly with lots of slipping. VSC might still kick in to try to keep the vehicle going in the direction you intend, or if not it might let you do donuts.

If you add a mechanical LSD, it can enhance the performance of the electronic system, since that's not perfect, but it may not be necessary or even desirable all the time. I don't know enough about them to say.

For off-road driving, a locking differential is likely better than a LSD, since LSDs generally need some resistance on the free wheel to work (it's limited slip, not no slip). For normal roads and slippery conditions, the built-in system should be enough most of the time.
 
Thanks for your response. I've continued to try and research this further on Tacoma forums, if a TrueTrac system can be installed with the stock Toyota Auto LSD and no one seems to know, which I find really odd. From what I understand thus far, the Auto LSD simply uses the brakes to control the slipping tire, whereas TrueTrac engages the other rear wheel so that both wheels have power, which to me would make a huge difference if that is correct.

I guess where the confusion still is, is that if installing a Detroit TrueTrac will interfere with the Auto LSD and VSC or vise versa. I'm still under the impression that the stock Auto LSD does not engage the other rear tire so that both are turning, correct?
 
Auto LSD does kind of engage the other tire. When it applies the brakes to the spinning wheel, that means power goes to the other wheel because of the way differentials work. But it does it in pulses. You won't really get smooth power when it's working, but it should be enough to get you unstuck. It seems like it's best at getting moving from a stop, and I'm not sure how well it works for normal driving.

A limited slip differential should help Auto LSD work better, as long as Auto LSD doesn't damage the differential. Auto LSD basically hammers on the brakes in pulses, which could put a lot of stress on the locking mechanism of a LSD since it will be repeatedly locking and unlocking. If Auto LSD kicks in before a mechanical LSD, you won't get as much benefit from the mechanical LSD. If the mechanical one kicks in first, you might never need Auto LSD.

I have 4WD, so I haven't used Auto LSD, but I've had the traction control help me out when I have the center differential locked. That turns off VSC, and as far as I can tell puts it in a mode similar to Auto LSD (but they don't call it that on 4WD). Auto LSD applies the brakes the same way as traction control, VSC, DAC, HAC, TRAC, A-TRAC or whatever. They are all just different things that the brake system can do to help you.

Why do you want a LSD, anyway? Is there anything you can't do with the stock setup? Have you tried Auto LSD and gotten it to activate? You will know when it activates, because it pulses the brakes really loudly!
 
m85476585 said:
Why do you want a LSD, anyway? Is there anything you can't do with the stock setup? Have you tried Auto LSD and gotten it to activate? You will know when it activates, because it pulses the brakes really loudly!
Click to expand...

Thanks again for the info.

I'm looking at a TrueTrac LSD because I have 2WD and live where it snows a little. I don't do any 4 wheeling but just wanted to have more sense of security that I wouldn't get stuck. I'm planning on purchasing some good AT tires but a guy at a local shop was telling me about Detroit TrueTrac and said it would definitely help to have both wheels turning in the rear. I guess we were both under the impression that the 2WD 4runner is always a one-legger unless an aftermarket LSD is installed. This is what lead me on this search to see if it is truly worth it or if it would just cause issues with the factory Auto LSD.
 
Try it out this winter, if you haven't tried it in snow before. You might find that the stock setup is good enough. A mechanical LDS is great for cars without traction control or Auto LSD (or cars with inferior traction control), but Toyota's electronic system on the 4runner is very good from what I understand.

The most important upgrade you can do for winter is snow tires. Stock 2WD with snow tires is better than 4WD with all season tires, 2WD with LSD and all season tires, etc. 4WD with all season tires might beat 2WD with snow tires in straight line acceleration on snow, but snow tires will greatly improve cornering and braking, which are arguably more important than acceleration.

There is an ongoing thread about AT vs snow tires in the 5th gen section:
http://www.toyota-4runner.org/5th-gen-t4rs/180701-best-meaty-tires-snow.html
 
m85476585 said:
Try it out this winter, if you haven't tried it in snow before. You might find that the stock setup is good enough. A mechanical LDS is great for cars without traction control or Auto LSD (or cars with inferior traction control), but Toyota's electronic system on the 4runner is very good from what I understand.

The most important upgrade you can do for winter is snow tires. Stock 2WD with snow tires is better than 4WD with all season tires, 2WD with LSD and all season tires, etc. 4WD with all season tires might beat 2WD with snow tires in straight line acceleration on snow, but snow tires will greatly improve cornering and braking, which are arguably more important than acceleration.

There is an ongoing thread about AT vs snow tires in the 5th gen section:
http://www.toyota-4runner.org/5th-gen-t4rs/180701-best-meaty-tires-snow.html
Click to expand...
I second this. I have not tried it yet (I'm in San Diego), but my extensive research suggests the Auto LSD in our trucks is actually pretty damn good in low traction situations. I will be testing it this winter.
 
m85476585 said:
Try it out this winter, if you haven't tried it in snow before. You might find that the stock setup is good enough. A mechanical LDS is great for cars without traction control or Auto LSD (or cars with inferior traction control), but Toyota's electronic system on the 4runner is very good from what I understand.

The most important upgrade you can do for winter is snow tires. Stock 2WD with snow tires is better than 4WD with all season tires, 2WD with LSD and all season tires, etc. 4WD with all season tires might beat 2WD with snow tires in straight line acceleration on snow, but snow tires will greatly improve cornering and braking, which are arguably more important than acceleration.

There is an ongoing thread about AT vs snow tires in the 5th gen section:
http://www.toyota-4runner.org/5th-gen-t4rs/180701-best-meaty-tires-snow.html
Click to expand...

Yea I guess I'll just wait until winter and see how it performs. I didn't realize the stock LSD system on the 2WD was decent.

I've narrowed my "snow tires" down between the Cooper ST MAXX and Wrangler Duratrac.
 
Of those two, the Duratracs are better for snow because they have more sipes (small grooves that wick away water and provide biting edges. Often zigzag shaped for stability), and because they have the mountain/snowflake rating, which means that they meet some very minimal requirements for snow performance.

If you expect to see more than a little snow, like going skiing on a regular basis, then a dedicated studless winter tire like Bridgestone Blizzak or Michelin X-ice would be much better. Check out photos of the Blizzaks to see the difference.

You should be able to find a tire shop that will swap over winter/summer tires for around $50 at the start end end of each winter.
 
Don't let the Auto LSD fool you into relying on it in certain situations since you are relying traction control which can cut power at the wrong time. BTW m85476585 you are wrong on the Duratracs they worked great in the 2 feet of powder this past weekend unlike my friends Blizzaks which worked great on the road but not so good when we hit the FSRs.
 
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Duratracs oh' ya!!

m85476585 said:
Of those two, the Duratracs are better for snow because they have more sipes (small grooves that wick away water and provide biting edges. Often zigzag shaped for stability), and because they have the mountain/snowflake rating, which means that they meet some very minimal requirements for snow performance.

If you expect to see more than a little snow, like going skiing on a regular basis, then a dedicated studless winter tire like Bridgestone Blizzak or Michelin X-ice would be much better. Check out photos of the Blizzaks to see the difference.

You should be able to find a tire shop that will swap over winter/summer tires for around $50 at the start end end of each winter.
Click to expand...


I have Duratracs on my 07 4wd Runner and without a doubt they are the best tires I've ever had. Ride super smooth, very quiet for a large lug tire (had Michelin all seasons, noise little difference there) and Duratracs tread through snow/mud at an unstoppable pace. I'll never buy anything else unless forced too. They are higher priced but it's for reasons deserved. Fantastic tires fwiw! :bravo: Goodyear
 
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