Real world difference between LSD & lockers

[Jbeeker]

I have a 2019 JLU with an open front & LSD rear. I have the Mopar 2.5” lift with 35” KO2’s. So far I’ve only used it on forest roads in Arizona in dry conditions - no major hills ... yet ... and I have no complaints. I don’t intend to use it for rock crawling. For me, my Jeep is simply the tool I use to get me to those peaceful and isolated camping sites I enjoy.

Does anyone have any real world experience with where I’m going to experience shortcomings with my current setup? Can I drive on relatively level forest roads in muddy/snowy conditions with it? What happens when I try to tackle a steep grade on loose gravel (or mud, or snow)? I don’t want to get lockers if I don’t need them (and I’d rather get my education here and not when I’m stuck on a trail).

The second part of my question is, what are the real world differences, between a LSD and lockers? I know the basics in that if a wheel loses traction a LSD will begin to apply power to the wheel with traction. If things get too bad, however, will a LSD eventually “give up” and start acting like an open diff? I know lockers have to have significant superiority over a LSD otherwise they wouldn’t exist. Phrased another way, can anyone provide me with scenarios where I’d get stuck with a LSD but I’d be OK with lockers?

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[InvertedLogic]

The biggest difference is when there is a wheel up in the air, or when 3/4 wheels have zero traction what-so-ever. As long as all 4 wheels are on the ground, you'll be fine - albeit with some wheel spin as one side spins slightly faster than the other as the LSD works.

Biggest difference imo is the front locker in the Rubi vs open in all of the other trims, but that's another conversation.

 

[Lapis]

A locker work by using some mechanism (electronic servo or air piston) to "lock" both axle shafts together, so that both wheels on the axle turn at the same speed when the locker is engaged.

A LSD works by using a system, such as clutch plates, springs, or helical gears (I'm not sure which the new Jeeps are using) to lock the two axles shafts together so that they spin at the same speed when a certain difference happens (usually one is spinning 100rpms faster than the other).

In theory, if both the locker or LSD are working as designed, once in a "locked" scenario, they are operating the same way (both wheels are turning at the same speed regardless of traction).

The only point where one would "give up" is if it fails and something breaks. Or the wheels haven't reached the threshold for it to apply.

 

[2Wheel-Lee]

In my experience, an LSD works well for slippery on-road conditions when moving, but shouldn't be relied upon for offroad conditions (especially from a stop) when one wheel doesn't have traction. The LSD will have some engagement for the wheel that has traction, but not much. The ability to get the wheel with traction turning is, well, limited (Limited Slip Differential).

One situation I remember years ago was with my Ram 2500. It has an LSD in the rear. I had to pull partially off the highway. The right side of the truck was partially in a snow bank, with apparently ice underneath. When I needed to get going, my right rear wheel just spun. Put it in 4WD, and then both the front and rear right wheels just spun. The wheels on the pavement did nothing. As did the LSD. I was stuck in the lamest situation. Applying the brake did help, but not enough, as the snow bank was holding me in more than I had expected.

When you absolutely need the wheel with traction to get full traction, you need a locker - selectable is preferred. If you're on a budget and can only afford one locker, generally you'd want to get the rear one first. Sure, many people can drive through technical offroad trails without lockers, but when you need a locker, you need a locker.

 

[Jbeeker]

In my experience, an LSD works well for slippery on-road conditions when moving, but shouldn't be relied upon for offroad conditions (especially from a stop) when one wheel doesn't have traction. The LSD will have some engagement for the wheel that has traction, but not much. The ability to get the wheel with traction turning is, well, limited (Limited Slip Differential).

One situation I remember years ago was with my Ram 2500. It has an LSD in the rear. I had to pull partially off the highway. The right side of the truck was partially in a snow bank, with apparently ice underneath. When I needed to get going, my right rear wheel just spun. Put it in 4WD, and then both the front and rear right wheels just spun. The wheels on the pavement did nothing. As did the LSD. I was stuck in the lamest situation. Applying the brake did help, but not enough, as the snow bank was holding me in more than I had expected.

When you absolutely need the wheel with traction to get full traction, you need a locker - selectable is preferred. If you're on a budget and can only afford one locker, generally you'd want to get the rear one first. Sure, many people can drive through technical offroad trails without lockers, but when you need a locker, you need a locker.

Great info! Thank you!!

 

[Karnak]

Unless I'm mistaken, the Torsen type LSD doesn't have a "slight give" before engaging the LSD like the other spring clutch plate types. Like others have stated, I'm not sure which type is in our JL but a LSD off-road is still very good and in a situation where its not gonna be an Iced pavement or very low friction point, it'll work very well. The locker can excel if the friction levels are extremely low because of the fact it doesn't have "give" before engaging and once its engaged, it works right away.

Without going with 2 lockers, you could still go with one activateable locker in the front and that combined with your LSD in the back would be almost on par with 2 lockers, just a tiny bit less in rare circonstances.

Also, all the situations you mention are situations where "constant momentum" during climb or obstacle crossing is important for success and as such, your wheels are all spinning and in that case your LSD would be engaged already anyways and most hills and loose rock uphill roads I did with my 2019 JL with lsd, I was able to navigate them with momentum and pedal control while choosing the correct lines for best traction (I did have to do take 2s and 3's on some, but thats just for adjusting my momentum by increments to pass it with just enough). Obviously the both lockers would make it easier, but if you don't want to put lockers, you don't really need to imo. you could also get a winch with a long cable and then if you can't get uphill, you winch the rest of the way etc. if your overlanding, a winch may be a better buy than lockers if your considering lockers. but I disgress.

 

[Karnak]

 

[Karnak]

 

[Jbeeker]

Unless I'm mistaken, the Torsen type LSD doesn't have a "slight give" before engaging the LSD like the other spring clutch plate types. Like others have stated, I'm not sure which type is in our JL but a LSD off-road is still very good and in a situation where its not gonna be an Iced pavement or very low friction point, it'll work very well. The locker can excel if the friction levels are extremely low because of the fact it doesn't have "give" before engaging and once its engaged, it works right away.

Without going with 2 lockers, you could still go with one activateable locker in the front and that combined with your LSD in the back would be almost on par with 2 lockers, just a tiny bit less in rare circonstances.

Also, all the situations you mention are situations where "constant momentum" during climb or obstacle crossing is important for success and as such, your wheels are all spinning and in that case your LSD would be engaged already anyways and most hills and loose rock uphill roads I did with my 2019 JL with lsd, I was able to navigate them with momentum and pedal control while choosing the correct lines for best traction (I did have to do take 2s and 3's on some, but thats just for adjusting my momentum by increments to pass it with just enough). Obviously the both lockers would make it easier, but if you don't want to put lockers, you don't really need to imo. you could also get a winch with a long cable and then if you can't get uphill, you winch the rest of the way etc. if your overlanding, a winch may be a better buy than lockers if your considering lockers. but I disgress.

Yan, thank you so much for all that good info! I’ll definitely consider a front locker and winch.

 

[mwilk012]

This makes me wonder how long it takes to wear the clutch packs out of a LSD, and how you would ever notice.

 

[Karnak]

This makes me wonder how long it takes to wear the clutch packs out of a LSD, and how you would ever notice.

It should normally take a long time since they're engineered for this and with the right oil, should not wear out that fast. in the old days, 200k was good to aim for a new set of clutch disks but nowadays, I'm not sure.

As for noticing; it would become more obvious when the "give" that one wheel requires before engaging the other would start to increase. As plates wear, the freespace increases and thus, when power is applied and tries to "turn" the other plates but friction is not high enough, they would not stick together "as much" and you'd notice one wheel spinning a bit more than before when the other is trying to work etc and the two wheels would not stick/turn complately together (at the same speed) all the time when its engaged. One wheel will turn "more" than before before engaging the other wheel when the clutch pack engages and to the point of complete wear, then one wheel would just spin without engaging the other wheel because the friction materials would not contact themselves hard enough (or at all) to create enough "grab" to turn the disks and thus would now act like an open diff. Hopefully my explanation makes sense.

 

[mwilk012]

It does, thanks!

 

[AZ Hella]

JLU sport here with the 6 speed.
I have been wheeling my JLU sport hard with the LSD for 13k miles. I have been very surprised with the performance. Also don’t forget the BLD system Is helping in the background. With a little bit of left foot braking and the LSD I haven't been stopped yet.

 

[CarbonSteel]

This makes me wonder how long it takes to wear the clutch packs out of a LSD, and how you would ever notice.

Based on the issues reported with LSD axles on this site, apparently not very long with many of them failing at less than 20K miles due to the clutch material contaminating the oil and accelerating wear to the point of failure. In the old days, depending on the use case, 150K miles was not usual.

 

[basinite]

Almost all my Jeeps, including a truck, have all had LSD rear ends and I've loved them all. With an LSD the rear end is pretty much always locked in and only disconnects when turning and/or letting off the gas. The only drawback to this is you need to be really careful on slick roads to avoid fishtailing.

Rubicon lockers are great, but Jeep doesn't trust their customers, so they only work in 4LO and not 4HI (barring you purchase a Tazer). This makes them almost useless for the 98% of us who don't rock climb in places like Moab and etc.

I have attached a link to a video of me driving my Jeep on a mountain road. On a road like this, I would take a Sport with a LSD any day over a Rubicon. On roads like this you have to keep up the speed or you will be stuck!!! 4HI not 4Lo, thus making Rubicon's lockers worthless in the real world.

For what you described you will be better served with a LSD, rather than lockers.

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