Auto LSD versus Rear Locking Differential

gudujarlson · Aug 11, 2025

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

soundman98 · Aug 11, 2025

GTGallop said: ↑

All forms of LSD are done with the intent that one wheel is spinning faster and breaking traction while one wheel is underpowered to catch up to the faster wheel.

So a mechanical LSD uses special additive in the fluid and a small clutch pack in the differential to temporarily arrest the slipping spinning wheel and divert the power to the slower underpowered wheel. In an Auto or Electronic LSD that clutch pack is replaced by sensors and a brake at the end of the wheel instead of the differential. But clutch pack or brake they do the same thing. The sensor and brake system is just a little more programmable and tunable.

While it is counter-intuitive to brake a wheel when you want to be going forward faster, that wheel was slipping traction and wasting horsepower - like air-conditioning with the windows open. You are just blowing all that cold air right out the window and the spinning wheel is blowing torque and horsepower right out the side if the truck in the form of over rotation. Meanwhile the wheel that does have good traction is getting less power or less propulsion. LSD shifts that wasted power to that wheel that has forward potential.

So is it faster with the nannies off or on? Depends on the situation. On the tarmac where both wheels have SOME traction (60/40 split) but there is an imbalance, taking the LSD off can benefit you. But this isn't a race truck. It's an off road truck. And off road your imbalance of power will be greater. Somewhere between 80/20 and 100/0. That's where LSD or Auto / E-LSD gets you moving forward faster. Also bear in mind that on the tarmac, "faster" is in 0-60 times, quarter miles, and running over 60MPH. On the trail, "faster" is 0-5 or going from stuck to moving. Same with in-climate weather like snow and ice. You aren't trying to go 80mph in the snow, ice, trail. Just going any at all is good.

Don't forget your truck comes with extra gears to make it go SLOW not fast. That's where the LSD shines.
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what about torsen LSD's?

Cetacean Sensation · Aug 11, 2025

soundman98 said: ↑

what about torsen LSD's?
Click to expand...

Helical LSDs (Torsen is a brand name) use a set of worm gears to move power around. They do not have clutches. Here's a good visualization of how they work.

That's why I'm so curious that nobody offers one inside a switched locker.

ShimStack · Aug 11, 2025

Amocat15 said: ↑

The way I understand is that with (normal setting) everything on, the VSC and LSD functions are both active. With a single press of the VSC off button, the VSC functions are disabled, leaving only LSD functions active. Then as mentioned above if you want to do donuts in the snow, long press of the button turns it all off. If I am mistaken please correct me!
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I think it's important to realize that the autoLSD function only exists in the autoLSD mode and traction control that is active in the normal mode with VSC is a bit different animal.

GTGallop · Aug 11, 2025

soundman98 said: ↑

what about torsen LSD's?
Click to expand...

MAN! That brings back a memory. Forgot all about those. I'll bet I haven't thought about a Helical LSD for 15 or 20 years.

Barsoom · Aug 12, 2025

Cetacean Sensation said: ↑

Helical LSDs (Torsen is a brand name) use a set of worm gears to move power around. They do not have clutches. Here's a good visualization of how they work.

That's why I'm so curious that nobody offers one inside a switched locker.
Click to expand...

My 2002 Isizu Axiom had a Torsen LSD, IIRC. It was unstoppable. In 4Low I could go on just about any trail in Alaska. In 4Hi/Torque On Demand (Borg-Warner center differential) I could fly thru a foot deep snow on the highway and never loose control.

soundman98 · Aug 12, 2025

GTGallop said: ↑

MAN! That brings back a memory. Forgot all about those. I'll bet I haven't thought about a Helical LSD for 15 or 20 years.
Click to expand...

i think about torsen LSD's most weekends.

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