LSD vs Traction Control

[grimmjeeper]

LSD = 4WD Auto correct?

Not always.

LSD is Limited Slip Differential. It's a mechanism inside the differential to help keep the tires on either side of the axle from free spinning. It is a purely mechanical system (clutches or helical gears) that has no direct computer control applied to it.

4wd auto is a setup in the transfer case to let you run 4wd on pavement without binding. It's essentially a differential inside the transfer case. In the JL, there is a computer controlled system to bias the torque and prevent slip.

4wd auto comes with open diffs. You can add LSD to one or both axles and it will help make the computer control more effective.

Some systems like QuadraDrive on the Grand Cherokee have a computer controlled torque biasing differential in each axle. That's different than a mechanical LSD. Adding that to a JL is more complicated than it's worth.

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[Wbino]

Not always.

LSD is Limited Slip Differential. It's a mechanism inside the differential to help keep the tires on either side of the axle from free spinning. It is a purely mechanical system (clutches or helical gears) that has no direct computer control applied to it.

4wd auto is a setup in the transfer case to let you run 4wd on pavement without binding. It's essentially a differential inside the transfer case. In the JL, there is a computer controlled system to bias the torque and prevent slip.

4wd auto comes with open diffs. You can add LSD to one or both axles and it will help make the computer control more effective.

Some systems like QuadraDrive on the Grand Cherokee have a computer controlled torque biasing differential in each axle. That's different than a mechanical LSD. Adding that to a JL is more complicated than it's worth.

So what is your opinion on the 4WD auto on some Wranglers?
When I ordered mine I just checked all the boxes. lol.
But I do notice I use slighty more gas in 4WD Auto than if I leave it in 2HI.
I'm have no mechanical knowledge so I do not know why that is.

 

[Steph1]

Traction control reduces engine output to stop wheel spin, whereas the lsd transfers some power from the spinning wheel to the one on the other side thats not spinning. TC is good for low traction situations on road where you might otherwise lose control of the vehicle, but it will get you stuck offroad. They're two different systems with two different purposes.

If you've only ever had open diff vehicles off road or in snow, the lsd is a game changer.

This^^^^^^ plus, the Selec-trac is the 4wd auto capable Sahara (Non-Rubicon) transfer case. The rear diff LSD is called the trac-lok and is definitely a plus for road vehicles, especially for those in slippery winter climates.

 

[jeepoch]

LSD = 4WD Auto correct?

Nope, not quite right. An LSD axle is always in limited slip independent of the transfer case lever setting. You can have some or even a lot of locking action in 2WD.

The LSD provides an automatic locker. Nothing to do with 2 or 4WD.

The response from @grimmjeeper above is the most accurate.

 

[jeepoch]

So what is your opinion on the 4WD auto on some Wranglers?
When I ordered mine I just checked all the boxes. lol.
But I do notice I use slighty more gas in 4WD Auto than if I leave it in 2HI.
I'm have no mechanical knowledge so I do not know why that is.

Walter,

Great question. Auto 4WD is a more sophisticated drivetrain altogether. It in a lot of ways, is more like an All-Wheel Drive (AWD) system

With auto 4WD, or sometimes referred to as partial 4WD, the transfer case automatically sends power to either the front, rear or both axles without any driver intervention. This mode works best in slippery or inclement weather where the best possible dynamic traction mode is selected automatically based on wheel slip and transfer case torque sensors.

However, in extreme situations or while off-roading it's generally always better to explicitly select full-time 4WD especially when 4LO is required.

Regardless, many top-of-the-line, off-road vehicles offer this transfer case as a luxury feature. It certainly comes with a higher expense. But once you get accustomed to it, you'll likely get spoiled by it.

Hope this helps explain Auto 4WD and how this differs from the auto locking, limited slip differential (LSD) axle. These are two totally separate things.

[Edit] Whoops forgot to address your gas mileage comment. Naturally, when in 2WD there are a lot less mechanically connected components within the drivetrain. Especially when the Front Axle Disconnect (FAD) is disengaged. The more wheels not receiving torque, generally the less load on the engine. Of course this savings really is found on straight and level pavement under normal driving conditions.

Naturally with the least mechanically connected things, lower powertrain losses are realized and fuel efficiency goes up. Driving around in either 'auto' or 'partial' 4WD will always require more energy from your power-plant than what 2WD can provide. The way cool toys come with a cost.

Watch how an EV 4xe application really suffers from an auto 4WD experience. While it may not seem like a lot in theory, driving around with all four wheels receiving power does provide more drive line resistance in the form of drag. If fuel efficiency is your ultimate goal, the solution for that is a boring ass, not very capable Prius.

Again, the way cool toys come with an expense.

Best regards,
Jay

 

[basinite]

Here is a quick video showing how both of these work in real life. Hope this helps you out.

 

[grimmjeeper]

Walter,

Great question. Auto 4WD is a more sophisticated drivetrain altogether. It in a lot of ways, is more like an All-Wheel Drive (AWD) system

With auto 4WD, or sometimes referred to as partial 4WD, the transfer case automatically sends power to either the front, rear or both axles without any driver intervention. This mode works best in slippery or inclement weather where the best possible dynamic traction mode is selected automatically based on wheel slip and transfer case torque sensors.

However, in extreme situations or while off-roading it's generally always better to explicitly select full-time 4WD especially when 4LO is required.

Regardless, many top-of-the-line, off-road vehicles offer this transfer case as a luxury feature. It certainly comes with a higher expense. But once you get accustomed to it, you'll likely get spoiled by it.

Hope this helps explain Auto 4WD and how this differs from the auto locking, limited slip differential (LSD) axle. These are two totally separate things.

One semantic point as far as terminology goes.

Typically, the 4wd for the road is called "full time". It is the mode that lets the front and rear run at different speeds when you're on the road. That's the 4wd auto that’s the option in the JL.

"Part time" 4wd is the mode where the front and rear driveshafts are locked together. This gives you better performance in low traction situations off road. The base configuration of the JL is part time in both 4wd hi and low.

 

[grimmjeeper]

You can also get a helical gear LSD which does NOT have clutch packs to wear out. It took me several weeks and lots of videos to understand how it works. It's pretty cool, bulletproof, and requires zero maintenance.
The military specifies helical LSD front and rear in almost all of their trucks and in all Humvees. It just works with no user intervention required which is important when somebody is shooting at you.

Helical LSD is sold by Eaton, Spartan, etc. Often called Detroit locker.
You can't buy one for the Dana 35/M200 axle in the base sport Wrangler.
If I had known better I would have made sure I had dana 44 axles so I could drop a helical inside.

I mentioned both clutches and helical gears in my post.

 

[apensity]

Best reply ever! Thanks for taking the time!

Dylan, et., al.,

Yes there is certainly a lot of confusion about the different systems and modes. Each have their specific use case(s). Let's see if I can do a good job at describing them:

<<<snip>>>

Jay

 

[COMike]

Question for you guys, I am gravitating towards putting a LSD into my rear (looking at the Nitro Helix, Helical Gear Limited Slip Differential) in my 2022 JL High Tide. Here is the link, Black Friday deal is very appealing: https://nitro-gear.com/nitro-gear-axle-helix-helical-gear-limited-slip-for-32-spline-dana-m220.html.

So, my question, will this work in my JL as is or do I need other parts (e.g. axel, etc.)? I have done my fair share of mods to 3 different Jeeps over my years, but I have not done anything like this. I would most likely look to a specialist/garage to install.

Thanks for any guidance and insight!

 

[stumblinhorse]

Question for you guys, I am gravitating towards putting a LSD into my rear (looking at the Nitro Helix, Helical Gear Limited Slip Differential) in my 2022 JL High Tide. Here is the link, Black Friday deal is very appealing: https://nitro-gear.com/nitro-gear-axle-helix-helical-gear-limited-slip-for-32-spline-dana-m220.html.

So, my question, will this work in my JL as is or do I need other parts (e.g. axel, etc.)? I have done my fair share of mods to 3 different Jeeps over my years, but I have not done anything like this. I would most likely look to a specialist/garage to install.

Thanks for any guidance and insight!

If you spend the winter in tabernash, you will learn to hate LSD as I have. On snow packed roads, which are most all roads in tabernash, lsd will kick your rear end to the side as the torque is different to each side in the rear. I would recommend dedicated snow tires if you are spending the winter driving around back roads in Grand County. My opinion is snow tires and not spending on an LSD.

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