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Discussion Starter · #1 ·
I know we don't know all the details yet, but the recent rumours indicate that the JLU Sahara is going to be getting an optional Selec-Trac transfer case with a full-time 4WD setting. The Rubicon has Rock-Trac with only part-time 4WD.

I was wondering if someone knowledgeable could explain the differences and advantages and disadvantages of each system.

I've heard some people say that Selec-Trac is better in ice and snow. Other people say that's only if you don't know what you're doing.

Correct me if I'm wrong, but my understanding is that with Selec-Trac, the centre differential doesn't lock. So all wheels can spin at different speeds. The system can apply more torque to the front or back axles depending on what's needed. Also there may be an option for a rear Limited Slip Differential (LSD). How does this affect things?

On the other hand, with Rock-Trac the centre differential locks in 4H, so that the front axles and rear axles have to spin at the same speed always(?). I'm not quite understanding this since the front and rear differentials are open in 4H, so the left and right wheels can still spin at different speeds? Does the sum of the back and front have to be the same? I'm so confused.

Also my main concern is how Electronic Stability Control (ESC), Traction Control (TC) and Anti-Lock Brakes (ABS) work when in Rock-Trac's 4H. Some things I've read on the internet seem to imply that these can't work when the axles are locked together. Are these features disabled when in 4H on Rock-Trac? That concerns me a lot because I drive a lot in ice and snow and need the added safety of ESC and ABS especially.

I've read the JK owner's manual, but it doesn't explain enough.

I have watched the Jeep videos on YouTube explaining each system. But I need more explanation. I will post the videos for others in a reply to this post.
 

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I've heard some people say that Selec-Trac is better in ice and snow. Other people say that's only if you don't know what you're doing.
There are 2 different types of Selec-Trac. There is Selec-Trac and Selec-Trac II. The original Selec-Trac had 2H, 4H Part Time, 4H Full Time, N, and 4L Part Time. Really, you can't go wrong with this 4WD system because it has pretty much every option.

Selec-Trac II on the other hand only has 2H, 4WD Auto, and 4L. 4WD Auto is basically a full time 4WD, but it can transfer up to 100% torque to the axle with the most traction if need be.

The only reason I explained this is because there is no real answer whether Selec-Trac is better or worse than Rock-Trac. A better question to ask would be whether 4H Full Time or Part Time is better, since that is the main difference between Selec-Trac II and Rock-Trac.

"Other people say that's only if you don't know what you're doing." This is correct. A Part Time system will always have more traction than a Full Time system because the front and rear axles are locked. It is the same with differential lockers; a locked diff will always provide more traction. However, whenever you lock a diff, you lose some maneuverability. The same is true with 4H Part Time.

To an inexperienced driver, a 4H Full Time system will behave pretty similarly to a 2WD system, except the vehicle will have better traction. The Part Time system behaves slightly differently since the axles are locked together.

In my experience, there has never been a time that I felt that my maneuverability was limited by the Part Time system, except maybe trying to make a tight turn at slow speeds. At higher speeds, I don't push the vehicle far enough to where my turning ability is limited because I feel like if I have to turn that quickly, I am driving too fast to begin with.

One disadvantage of Part Time is for roads with only patches of snow/ice. While it probably isn't necessary, I disengage 4WD whenever I am on pavement, wet or not. So there could be situations where you are constantly going back and forth between 4H and 2H if you have a Part Time system. Shift-on-the-fly makes this process relatively painless, but some people don't like having to shift at all, so they prefer a 4H Full Time system that can be driven on pavement so they don't have to shift at all.

If I had to choose between having either 4H Part Time or Full Time, I would choose Part Time in a heartbeat. It gives you more capability. However, the original Selec-Trac offered both 4H Part Time and Full Time, so that would be ideal since you have both options.

Correct me if I'm wrong, but my understanding is that with Selec-Trac, the centre differential doesn't lock. So all wheels can spin at different speeds. The system can apply more torque to the front or back axles depending on what's needed. Also there may be an option for a rear Limited Slip Differential (LSD). How does this affect things?
For Selec-Trac II, you are pretty much correct. Selec-Trac II does allow you to lock the center diff if you put it in 4L, but then your speed is limited, and I would not recommend that for extended driving in the snow. The original Selec-Trac did have a 4H Part Time option in addition to 4H Full Time option.

LSD will give you better traction 100% of the time without affecting your handling ability as opposed to a locker which will affect your handling ability. However, it again comes down to driver experience.

If you manage to get your tires spinning in the snow with LSD, you are more likely to slide around because both tires on the axle are spinning. If just one tire was spinning like in an open diff, the other tire would still have grip on the road, so you retain some side-to-side stability. In other words, donuts are much easier with LSD. The good news is that you can still control the vehicle if you know what you are doing.

LSD in the rear will cause the rear end to kick out more if you give it to much gas, and LSD in the front will cause more understeer if you give it too much gas.

I have LSD in both the front and the rear. The easiest way to regain control is to let off the gas. However, sometimes that is not enough. As an example, I was driving in the snow in 2WD with LSD. I was doing some fishtails, but I was too aggressive with it and ended up fishtailing back and forth (an inexperienced driver would have crashed easily). I let off the gas, but it still took some time to regain traction. What I realized is that because I drive a manual, letting off the gas was not enough because the engine was still connected to the wheels, and the engine did not slow down fast enough. If I had hit the clutch sooner, the wheels would have slowed down much more rapidly, and I would have regained control sooner. Lesson learned.

On the other hand, with Rock-Trac the centre differential locks in 4H, so that the front axles and rear axles have to spin at the same speed always(?). I'm not quite understanding this since the front and rear differentials are open in 4H, so the left and right wheels can still spin at different speeds? Does the sum of the back and front have to be the same? I'm so confused.
This is probably just semantics, but there is no center diff in the Rock-Trac. It is just as transfer case.

Yes, the front/rear driveshafts are locked together and will always spin at the same speed. There is sort of a sum game. In an open diff, the driveshaft will spin at a speed proportional to the sum of the speed of each wheel on the axle. If you jack up both wheels and spin one of them, the other wheel should spin in the opposite direction, and the driveshaft should remain still because the sum of each wheel (a positive and a negative) cancels each other out. That is why the left/right wheels can still spin at different speeds in 4H.

Also my main concern is how Electronic Stability Control (ESC), Traction Control (TC) and Anti-Lock Brakes (ABS) work when in Rock-Trac's 4H. Some things I've read on the internet seem to imply that these can't work when the axles are locked together. Are these features disabled when in 4H on Rock-Trac? That concerns me a lot because I drive a lot in ice and snow and need the added safety of ESC and ABS especially.
From experience, ESC and TC absolutely work. In fact, they work so well that I intentionally disable them when driving in adverse weather because they are so unpredictable. I feel much more comfortable driving my own vehicle than to have it drive for me because it always catches me by surprise and does something that I don't want it to do. It works exactly as intended; I just don't like it.

As for ABS, I never really thought about it, but the concept does make sense. The front brakes can control both the front and rear tire speeds in 4H, so while the front ABS is trying to control the front wheels only, it is inadvertently controlling the rear wheels as well, but the rear brakes are doing the same thing. I could see how the computer could get confused. I am not saying it is true, but it wouldn't surprise me.

However, whether ABS works in 4H Part Time or not is a moot point. If you are using 4H, you don't want ABS. It is a proven fact that on low traction surfaces such as snow, dirt, etc., ABS actually increases, not decreases, stopping distance, and it doesn't even give you improved control either. If you slam the brakes on a 2WD car with ABS in the snow, it will behave almost identically to the same car with no ABS. When you are stopping that quickly in low traction terrain, no computer system in the world can prevent the wheels from sliding. Since you only use 4H Part Time on these types of surfaces, it is actually beneficial to you if the ABS does not work.
 

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Discussion Starter · #7 ·
Thank you for the detailed response turnbull.

I'm okay with shifting back and forth from 2Hi to 4Hi on the fly as I encounter ice/snow and dry pavement and ice/snow again, or if I need to make a sharp turn at speed.

My main concern is that ESC still be working in 4Hi in Rock-Trac. I know you said you didn't like it, but I find it very valuable. It has been very useful to me in my current front-wheel drive car, and I definitely want it working. I tested it out once in an empty parking lot full of ice and snow and just could not lose control, even as I tried.

I found this paper from 1988 on ABS for part-time 4WD systems. Presumably Fiat-Chrysler has had a chance to work on this problem since then. :)

Four Wheel Anti-Lock Brake System (ABS) for Four-Wheel Drive Vehicles

I've been saving up for a while now for a 2018 (or maybe 2019) Rubicon 4-dr, and I had my heart set on it, but now that the Sahara is getting Selec-Trac, I just wanted to learn more about it and completely understand both systems before I make a decision. The Sahara seemed like the luxury street version with the bling rims to me, which is not what I was going after. I want to do some off-roading, but I also live in a severe winter area (central Alberta). I regularly have to do highway driving at speed through blizzards, and sometimes that can be a bit dicey when the snow piles up. Don't want to spin out into the ditch.

I just wanted to know what I'd be losing by going with the part-time Rubicon vs the full-time Sahara. I've never owned a 4WD before so I'm not sure how the locked centre transfer case will affect handling in ice and snow, compared to an open centre. Is there much of a chance it will cause increased wheel slip and loss of control? I wanted to understand why many folks were saying that the full-time 4WD was better in winter.

I definitely would like my new Jeep 4x4 to be better in winter than my current fwd car.

And before anyone brings it up, yes, I always put good winter tires on all my vehicles. I plan on getting the very best for the new Jeep.
 

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Discussion Starter · #8 ·
Quick question: If you were driving on a fast highway through a severe blizzard, with heavy snow on the ground and ice underneath, and you had each of the following options, would you be in 2hi, pt-4hi or ft-4hi, and why?
 

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Sorry I didn't see this yesterday as I was out goofing... errr... golfing and then movies and star gazing with the roof down, so just answered reply posts when I've had a chnace not new ones.

But turbull pretty much covered it very well.

The only omitted bits or stuff I'd add, are;

Fulltime 4WD is good for those snowy, icey or torrential highways , where even rain on oily roads can be a concern at speed. Where you have to go fast, there is no option and you become a hazard if you are going slow. That's when FT4WD lets you have the confidence o all 4 wheels but nit worry about even the theoretical poissibility of binding or damage/wear to the system (never had an issue and I travel mountain oasses in PT4WD @ 120Kmh/75MPH all the time with the current Wrangler TC where arcing rolling blindish curves that are patchy with ice or snow to one half of the lane variable is quite common (especially through Banff), and shifting into 4Hi @ 75 is as much not an option as slowing down (it's a major artery so there's semis and everyone favourite foreign toruist seeing the mountains on the road too and can bee fully snow covered yet in full operation).

As for your question about disabled ABS and Traction control, that's only in 4Lo, which is a good thing, because they would cause traction loss when you've told the system that both you want the most grunty capable traction it can offer, and also... "here hold my beer" so the system gets out of your way.

As for what I'd chose on the highway it would depend on the road, super severe conditions all over then Part Time of current system, variable conditions with patchey but severe ice/snow build up for major chunks, even a mile/km stretch at a time then bar and back again, then FullTime.

For me, the best suited combos for the conditions (and this is my opinion based on decades of experience for me, no need for an argument about this like the LSD /Locker discussions) are;

Variable traction highway: FT4x4 with LSD

Terrible Highway conditions, 1 inch over everything and questionable underneath that: PT 4Hi + LSD.

Deep Snow off-road: PT 4Hi or Lo and with Lockers (especially if you can flash your lockers in 4H), but you gotta know how to drive this you can get SUPER stuck and also damage your rig if you dunno what you're doing.

That's why I like the idea of Selec-Trac but with an old TJ Rubicon (or new Eaton) style diff that can be locked but also has an LSD.

It would be nice to have. 4:1 Selec-Trac 4Lo ratio, but that's the only major advantage of the RockTrac, and the old SelectTrac wasn't as tough as the RockTrac, not that it's weak it jphas a great torque rating and durability history. Just that they beefed up the NV241OR for the Rubi even compared to the Sahara. But the new SelecTrac will likely be tougher than the old one simply because of modernity... but they could F it up, I just think better of Jeep/FCA though others mught disagree.
 
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Some additional good info about Selec-Trac internals and then other Jeep Transfer Cases...

1998 Jeep Grand Cherokee ZJ - NP242 HD SYE Transfer Case

HD NP242 Transfer Case Build - Super-Duty NP

Jp’s Guide To Jeep Transfer Cases - Jp Magazine

The Selec-Trac NV242, is almost exactly an VN241 with a mechanically clutch plate diff stuck inside, look at even the footprint. So you can activate all the Command-Trac, stuff, plus add a Full-Time option at no loss of functionality.
I like That, so always Selec-Trac for me as I'm not running such an over the top setup where I know I need the 4:1 ratio like for big tyre (that likely already have a bigger axle ratio) or possible added durability.

The nice thing is even the disparity of 2.72:1 vs 4:1 is somewhat mooted or at least muted by the larger first gear ratio and larger overall ratio soread of the new ZF 8-speed transmission, which will give both a 'respectable' crawl ratio, especially vs the current manual tranmission candidates.

But balls to the walls extreme off-roading is still gonna go to the RockTrac, that can just amplify the 4:1 ratio with stock 4.1:1 Axles and that 5:1 ZF first gear, offering an impressive 82:1 Crawl ratio.
 
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My main concern is that ESC still be working in 4Hi in Rock-Trac. I know you said you didn't like it, but I find it very valuable. It has been very useful to me in my current front-wheel drive car, and I definitely want it working. I tested it out once in an empty parking lot full of ice and snow and just could not lose control, even as I tried.
Just to clarify, ESC works in 4WD. It does what it is supposed to do. Traction control is disabled in 4H by default but can be reenabled by the driver, and ESC is enabled by default but can be disabled by the driver. In 4L, ESC and traction control are disabled by default but can be reenabled by the driver.

I found this paper from 1988 on ABS for part-time 4WD systems. Presumably Fiat-Chrysler has had a chance to work on this problem since then. :)

Four Wheel Anti-Lock Brake System (ABS) for Four-Wheel Drive Vehicles
At the end of the day, the terrain is going to dictate whether ABS will function properly or not. Low traction surfaces cause ABS systems to not work as intended. Since you only use 4WD Part Time on such surfaces, you do not need to worry about the 4WD causing the ABS to not function properly since the terrain is already going to do exactly that.

I just wanted to know what I'd be losing by going with the part-time Rubicon vs the full-time Sahara. I've never owned a 4WD before so I'm not sure how the locked centre transfer case will affect handling in ice and snow, compared to an open centre. Is there much of a chance it will cause increased wheel slip and loss of control? I wanted to understand why many folks were saying that the full-time 4WD was better in winter.
If you think you need a Rubicon for whatever offroading you do, then get a Rubicon. It will perform fine in the snow.

If you aren't doing serious offroading that would require lockers, then just get the Sahara. That way, you will have the option of 4H Full Time, and a rear LSD from the factory (if they offer this option like they do on the JK where non-Rubicon models can opt for an LSD). If nothing else, you will save yourself some money on features you don't need (lockers, 4:1 transfer case, etc.)

That is my opinion anyway.
 

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Discussion Starter · #12 ·
Thank you for all the responses guys. This is very helpful.

I have some followup questions, but will post them tomorrow maybe.
 

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Discussion Starter · #13 ·
Hey guys, so a few followup questions:

1. What would a rear LSD do for you in the blizzard highway scenario? Is it an advantage or disadvantage there?

2. The 2017 JK Owner's Manual says that you can shift on the fly back and forth between 2H to 4H. However, it doesn't mention any maximum speed at which you can do this. On the website there is a FAQ blurb for Rock-Trac that mentions the maximum speed for shifting on-the-fly to be 55 mph (88 kph). Is the information on the FAQ still relevant if it's not in the latest manual?

3. Theoretically speaking, what bad things would happen if you tried to shift at over 55 mph (88 kph)? And is it equally bad to shift from 4H to 2H as it would be from 2H to 4H?

4. Is there a maximum speed for being in 4H that you wouldn't want to go over?
 

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Hey guys, so a few followup questions:

1. What would a rear LSD do for you in the blizzard highway scenario? Is it an advantage or disadvantage there?
We both can likely direct you to a dozen threads with conflicting advice on the subject...that get a little 'heated'. :censored:

I personally prefer LSD for blizzardy highway, and would love to add FT4WD to that equation. However, as I NEED a locked rear sometimes for going up ski hills in snow/ice and spring & fall mud, that's what I have.
But I would prefer both options, like the TJ Rubi, as I mentioned earlier.

2. The 2017 JK Owner's Manual says that you can shift on the fly back and forth between 2H to 4H. However, it doesn't mention any maximum speed at which you can do this. On the website there is a FAQ blurb for Rock-Trac that mentions the maximum speed for shifting on-the-fly to be 55 mph (88 kph). Is the information on the FAQ still relevant if it's not in the latest manual?
Yes that still applies, there has been no change to the transfer case to improve high speed gear meshing.

3. Theoretically speaking, what bad things would happen if you tried to shift at over 55 mph (88 kph)? And is it equally bad to shift from 4H to 2H as it would be from 2H to 4H?
The issue is with the gears spinning at a higher speed trying to mesh, there's a greater chance of them not meshing or that mis-mesh causing damage, and resulting in either actually breaking a tooth or just smoothing the ends from a bunch of partial failed attempts which is also bad. Also it can put stress on the chain and could break it or stetch it, thus loosening it. There are many examples of these types of repairs out there.
Going from 4Hi to 2Hi can be done at higher speeds, it's engagement not disengagement that is the biggest concern, however stating them both as in/out avoid dumb people claiming confusion.
Many people claim doing this at faster speeds with no issue, but why stress the system unless you have an emergency reason? I never felt the need to test the limits at the cost of potential damage.

4. Is there a maximum speed for being in 4H that you wouldn't want to go over?
I would say try to keep it 80 and below if you can, but I regularly have it near 85MPH (135KPH), and occasionally above 90 to pass (144+) without issue on 5 JK(U) Wranglers over the past decade. There's no technical reason for speed to be an issue once locked in gear, because even the theoretical issue of binding and drivetrain wear is negated by the speed of the system, binding is more of an issue at low speeds, especially low soeed turns.

Hope that helps clarify things.
 

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I would say try to keep it 80 and below if you can, but I regularly have it near 85MPH (135KPH), and occasionally above 90 to pass (144+) without issue on 5 JK(U) Wranglers over the past decade. There's no technical reason for speed to be an issue once locked in gear, because even the theoretical issue of binding and drivetrain wear is negated by the speed of the system, binding is more of an issue at low speeds, especially low soeed turns.

Hope that helps clarify things.
quote that. If you go on a straight path, say a highway, I do not see why speed is a issue at all. If you try to do rally-style roads then yes, speed with a traditional 4WD is an issue and one needs a center viscouse junction to prevent binding.
 

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Discussion Starter · #16 ·
I personally prefer LSD for blizzardy highway, and would love to add FT4WD to that equation. However, as I NEED a locked rear sometimes for going up ski hills in snow/ice and spring & fall mud, that's what I have. But I would prefer both options, like the TJ Rubi, as I mentioned earlier.
I guess there's no way to turn off the LSD in the Sahara?

Is it true that the clutches in the LSD wear out (after how many miles approximately?) and that after that it behaves like an open diff? How expensive is it to fix or replace when that happens?

The issue is with the gears spinning at a higher speed trying to mesh, there's a greater chance of them not meshing or that mis-mesh causing damage, and resulting in either actually breaking a tooth or just smoothing the ends from a bunch of partial failed attempts which is also bad. Also it can put stress on the chain and could break it or stetch it, thus loosening it. There are many examples of these types of repairs out there.
Going from 4Hi to 2Hi can be done at higher speeds, it's engagement not disengagement that is the biggest concern, however stating them both as in/out avoid dumb people claiming confusion.
Many people claim doing this at faster speeds with no issue, but why stress the system unless you have an emergency reason? I never felt the need to test the limits at the cost of potential damage.
I was just asking for the case of some hypothetical emergency where you might want to switch from one to the other.

Also, don't transmissions have rev-limiters? Couldn't they design something that would block a change above a certain speed to prevent damage?


There's no technical reason for speed to be an issue once locked in gear, because even the theoretical issue of binding and drivetrain wear is negated by the speed of the system, binding is more of an issue at low speeds, especially low soeed turns.
Is that because presumably at high speeds you can't turn sharp enough to encounter binding, or is it some other reason?
 

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I guess there's no way to turn off the LSD in the Sahara?
Correct, it's mechanical, without a selector, and activated when a mechanical imbalance engages it auto-magic-ally. ;)

Otherwise it stays out of the way, which is nice, less thinking/worrying.
But if like some people you don't like how it works/acts/feels then you can always go the Rubi route which is open unless selected, or just plain open which is standard on both Sport, and which is how the Rubi would be on the highway.

Is it true that the clutches in the LSD wear out (after how many miles approximately?) and that after that it behaves like an open diff? How expensive is it to fix or replace when that happens?
Anything can wear out, I have not heard of it being a specifically prevalent issue.
Subaru centre and axle diffs can wear out too especially on the WRX STI, so it can happen to anything that puts torque down that way.

I was just asking for the case of some hypothetical emergency where you might want to switch from one to the other.
For a scenario where you're going above 55/88 and need to go from 2Hi to 4Hi, then slow down briefly to allow you to engage safely, or if you are already on ice then take your foot off the accelerator and cost to about 90 and then go, do your best to reduce the risk of damage.

I can't think of a high speed emergency needing to switch out of 4Hi, usually the "gotta switch out 4Hi" moments are slow speed when you forget to disengage when turning into a parking lot or some other bunding prone scenario.

Also, don't transmissions have rev-limiters? Couldn't they design something that would block a change above a certain speed to prevent damage?
Easier on electronic than a manual shifter lever. Also if they put that in there, and then you tried to engsge and it didn't work when you thought you were going 55 (though really 59) and your resultant delay or lack of 4Hi resulted in an accident... then who do you think is going to pay?
If you shift into 4Hi @ 90MPH and damage the Transfer Case you're likely to pay, but even if you can convince FCA to pay (either to get rid of you or because they believe you) then the most they pay is coupla hundred, not a coupla million.

Is that because presumably at high speeds you can't turn sharp enough to encounter binding, or is it some other reason?
That and the effects on the system and tyres' contact pad are diminished by their angular momentum so they aren't going to be stuck in place for very long exerting large forces and feedback, unlike at slower speeds. Also the turn are usually more gradual. But even on an off-ramp where turns are tighter, I've never had an issue, it's just not sharp enough.
Whereas a 90 degree turn at an intersection, or tight parking lot maneuvering could easily see the outisde tires turning at multiples of the inside tires, plus front and rear differences too, which is the TC's issue, that's where you experience binding the most.
 

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Correct, it's mechanical, without a selector, and activated when a mechanical imbalance engages it auto-magic-ally. ;)

Otherwise it stays out of the way, which is nice, less thinking/worrying.
But if like some people you don't like how it works/acts/feels then you can always go the Rubi route which is open unless selected, or just plain open which is standard on both Sport, and which is how the Rubi would be on the highway.
Just wanted to add to this, but my response is directed towards the OP since I know you probably already know everything I am about to say.

The LSD option in Wranglers is a TracLok, which is a clutch based system. They do wear out eventually, and their performance will degrade over time even before they are completely worn out.

You can get an aftermarket LSD known as the TrueTrac, which is a gear based system. These do not wear out, but they are more expensive. It'll cost you about $1000 to have one installed for parts and labor, but if you don't get the factory LSD, that'll save you some of that cost.
 

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1. What would a rear LSD do for you in the blizzard highway scenario? Is it an advantage or disadvantage there?
I think it comes down to preference, but one thing is for sure: the LSD will give you more traction. If you say blizzard, to me that means deep snow where you need as much traction as possible. I would want LSDs.

That said, all JKs (and I am sure the JLs) have Brake Lock Differential (BLD). This system uses the brakes to provide similar effects as an LSD, but it is not a true replacement.

There have been heated arguments as to whether an LSD is better than BLD, so I won't get into that. What is not debatable though is the LSD + BLD will provide more traction than just BLD, and BLD alone will provide more traction than no BLD or LSD.

However, you could argue that the LSD doesn't provide as much of a benefit on a Wrangler with BLD than one without BLD. A Rubicon may not have an LSD, but it does have BLD in the front and rear, so even with its open diffs, the Rubicon should perform fine in the snow.

There is one clear advantage of LSD over BLD. The LSD is proactive, whereas the BLD is reactive. The BLD requires wheel spin to activate. The LSD can transfer torque without any wheel spin, effectively making it harder for the wheels to break traction.
 

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Discussion Starter · #20 ·
Just curious, but are the electronic limited-slip differentials in the Grand Cherokee better than mechanical limited-slips like the TrueTrac?

The electronic ones seem to give you total control because (I think) one can control exactly the amount of slip and torque transfer to allow dynamically. But I guess it all has to be run by a computer program. Given that it needs computer control, I guess it wouldn't not be possible to install one on a vehicle that wasn't already equipped with it from the factory. Or at least it would be very difficult to do so because you'd have to connect it to the computer somehow and install software to make it work. Please correct me if I'm wrong.

Not that I'm looking to do that. If I wanted one I'd probably buy a Grand Cherokee instead. I was just wondering and trying to understand the different types of LSDs better.
 
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