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Discussion Starter · #1 ·
Hey all,
I am the happy new owner of a 2012 JKU Sahara. I want to say that reading this forum was part of my push to get one. I’ve learned so much in here and you all seem like such positive and happy people. Happy Jeep owners. Jeep feels like a family, that’s super cool. I’ve owned many different Audi’s and today I learned the difference between AWD and 4x4. I hopped in my Jeep excited to turn on the 4WD because I’ve been looking up how to work it. I turn it and try to move out my parking space and go left and she starts moving super funky and then I try and go right and it’s like the front wheels going up and down doing there own thing. I turn her off immediately and freak out. Then I put here back in 2H from 4H and hop out and look at my suspension all crazy (again I’ve only had AWD cars). I get back in the truck and everything is smooth. I quickly hopped into the forum and from there I was just like, let me sign up. I got a whole personal scenario and question to ask lol. I just don’t want to hurt anything. She’s fine right? I’ve read that you can destroy the drivetrain and all this bind stuff. My drivetrain is all good right?
 

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Welcome to the forum, and your Jeep is fine. And you learned the lesson that your Wrangler's full time 4WD isn't to be used on pavement. This is because the transfer case locks the front and rear driveshafts together, meaning the front and rear axles have to spin at the same rate. When you turn, the rotation rate changes in the front (due to the turn radius), so this causes the front and rear axles to fight each other until a tire slips somewhere to make up the difference.

Doing this at low speed for a short time like you did won't cause any harm, the drivetrain is tough. But definitely don't go driving down the road like that as it could break something at higher speeds, or at the least put undue wear on components.

If you use 4WD off road on a dirty, gravelly, muddy, etc surface, tires will always have some give to keep things from binding up.

Some people try to use 4WD on the pavement in the rain, and really that isn't advisable either because you'll likely still have plenty of grip and thus still run into binding, and there also isn't really a need for it because you're generally not just sliding all over the place only due to wet pavement (if you are, you need better tires). You can use it on snow, although need to be careful if it's just light snow where you have alternating dry pavement and patches of snow, because again the dry sections could cause binding.

Your Audi's AWD system is designed to work on the road by having open differentials between front and rear, allowing different rotation rates. AWD systems are generally better for driving on roads including slippery conditions. But the 4WD in your Wrangler is better off road because you always have power going to each axle, whereas with an open center diff once one wheel starts spinning you start losing power to all other wheels. Certain electronic systems can counteract that so may not be entirely the case, but the general rule applies.

Note your Sahara still has open diffs at each axle front and rear, so that once a tire starts spinning on one axle, the other wheel on that axle will start to lose power even if it has grip. But you'll still have the other axle, at least until you start spinning there too. This is where a locking axle differential (found on the Rubicons stock, but can be added to any Wrangler using aftermarket parts) comes into play, by locking the left and right wheels on an axle together, so that you maintain full power to both wheels at all times, useful for example if rock crawling with a wheel in the air.

But your Sahara and does have the electronically controlled Brake Lock Differential (BLD) which will automatically apply some braking force to a spinning wheel, to allow power to go to the other wheel. A differential allows the same torque to go to each wheel, so you're limited by whichever wheel spins most freely. By braking the loose wheel, the amount of torque that can be applied to the other wheel (which has traction) increases. So the BLD system helps you in situations where you might otherwise get stuck, and works pretty well. Basically once you get stuck you just slowly give it more gas (carefully, don't go crazy) and the system will try to do its work to get you going forward. It's not as good as a mechanical locker, but still pretty good.

Anyways, there's your crash course on 4WD and differentials, there's plenty more that could be said but I've already typed a lot!
 

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Discussion Starter · #3 ·
Welcome to the forum, and your Jeep is fine. And you learned the lesson that your Wrangler's full time 4WD isn't to be used on pavement. This is because the transfer case locks the front and rear driveshafts together, meaning the front and rear axles have to spin at the same rate. When you turn, the rotation rate changes in the front (due to the turn radius), so this causes the front and rear axles to fight each other until a tire slips somewhere to make up the difference.

Doing this at low speed for a short time like you did won't cause any harm, the drivetrain is tough. But definitely don't go driving down the road like that as it could break something at higher speeds, or at the least put undue wear on components.

If you use 4WD off road on a dirty, gravelly, muddy, etc surface, tires will always have some give to keep things from binding up.

Some people try to use 4WD on the pavement in the rain, and really that isn't advisable either because you'll likely still have plenty of grip and thus still run into binding, and there also isn't really a need for it because you're generally not just sliding all over the place only due to wet pavement (if you are, you need better tires). You can use it on snow, although need to be careful if it's just light snow where you have alternating dry pavement and patches of snow, because again the dry sections could cause binding.

Your Audi's AWD system is designed to work on the road by having open differentials between front and rear, allowing different rotation rates. AWD systems are generally better for driving on roads including slippery conditions. But the 4WD in your Wrangler is better off road because you always have power going to each axle, whereas with an open center diff once one wheel starts spinning you start losing power to all other wheels. Certain electronic systems can counteract that so may not be entirely the case, but the general rule applies.

Note your Sahara still has open diffs at each axle front and rear, so that once a tire starts spinning on one axle, the other wheel on that axle will start to lose power even if it has grip. But you'll still have the other axle, at least until you start spinning there too. This is where a locking axle differential (found on the Rubicons stock, but can be added to any Wrangler using aftermarket parts) comes into play, by locking the left and right wheels on an axle together, so that you maintain full power to both wheels at all times, useful for example if rock crawling with a wheel in the air.

But your Sahara and does have the electronically controlled Brake Lock Differential (BLD) which will automatically apply some braking force to a spinning wheel, to allow power to go to the other wheel. A differential allows the same torque to go to each wheel, so you're limited by whichever wheel spins most freely. By braking the loose wheel, the amount of torque that can be applied to the other wheel (which has traction) increases. So the BLD system helps you in situations where you might otherwise get stuck, and works pretty well. Basically once you get stuck you just slowly give it more gas (carefully, don't go crazy) and the system will try to do its work to get you going forward. It's not as good as a mechanical locker, but still pretty good.

Anyways, there's your crash course on 4WD and differentials, there's plenty more that could be said but I've already typed a lot!



See, THIS is what I’m talking about. THIS is why I love this forum. Thank you so much. This was definitely a learning moment as a whole. Thank you for your time. Yes I just wanted to be sure I do nothing wrong, I treat her like a baby, it’s only been about 2 weeks, and I was freaking out. Thank you.
 

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See, THIS is what I’m talking about. THIS is why I love this forum. Thank you so much. This was definitely a learning moment as a whole. Thank you for your time. Yes I just wanted to be sure I do nothing wrong, I treat her like a baby, it’s only been about 2 weeks, and I was freaking out. Thank you.

Glad to help! I was in your shoes about 2 years ago when I got my Jeep, which is my first 4WD vehicle. Have learned a lot on this forum, including asking a lot of my own questions.
 

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Yep, 4WD is only for snow, mud, if you’re loosing traction/getting stuck, and off road.
And in those situations 4WD >> AWD.
 

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Hey all,
I am the happy new owner of a 2012 JKU Sahara. I want to say that reading this forum was part of my push to get one. I’ve learned so much in here and you all seem like such positive and happy people. Happy Jeep owners. Jeep feels like a family, that’s super cool. I’ve owned many different Audi’s and today I learned the difference between AWD and 4x4. I hopped in my Jeep excited to turn on the 4WD because I’ve been looking up how to work it. I turn it and try to move out my parking space and go left and she starts moving super funky and then I try and go right and it’s like the front wheels going up and down doing there own thing. I turn her off immediately and freak out. Then I put here back in 2H from 4H and hop out and look at my suspension all crazy (again I’ve only had AWD cars). I get back in the truck and everything is smooth. I quickly hopped into the forum and from there I was just like, let me sign up. I got a whole personal scenario and question to ask lol. I just don’t want to hurt anything. She’s fine right? I’ve read that you can destroy the drivetrain and all this bind stuff. My drivetrain is all good right?
As mentioned, your drive train is fine.
And for future reference, every time someone calls a Jeep a car God kills a kitten, and every time someone calls a Jeep a truck She kills a puppy.
Jeeps are Jeeps, neither car nor truck.
Welcome to the club.
 

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And for future reference, every time someone calls a Jeep a car God kills a kitten, and every time someone calls a Jeep a truck She kills a puppy.
Jeeps are Jeeps, neither car nor truck.
So is the JT a Jeep or a truck?
 

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Some people try to use 4WD on the pavement in the rain, and really that isn't advisable either because you'll likely still have plenty of grip and thus still run into binding, and there also isn't really a need for it because you're generally not just sliding all over the place only due to wet pavement (if you are, you need better tires)
That first heavy rain after a few days of the hot sun and my Mud Terrain Tires need some help when I try to pull out quickly into traffic. (see above: need new tires ;)) There have been a number of times I have put it in 4x4 just to pull out without spinning the rear inside tire while turning into the traffic flow. As soon as I'm lined up straight I go back to 2 wheel drive. I've done this less than 6 times in 2 years.

Even on the trails you will be switching from 2 wheel drive to 4 as necessary. Then back to 2 wheel drive. I have a Rubicon and have only needed to lock in the front and rear once.
 
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It's like a modern El Camino. Only made by Ford. And probably upside down.
Flushes anti-clockwise as well.

I think it got discontinued recently. They're so ugly they're pretty --- know what I mean?
 
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