BLD'sFTW!

OK, I wasn't sure where to put this info so I will put it here as a write up. Here is a speech I have given many many times and Maverick loves to hear it.


ESP tries to correct for you using the brakes to keep you pointed in the right direction and not turn over. The traction control system doesn't want your wheels to spin, so it cuts power, applies brakes to keep that from happening. BLD, (brake lock differential,) doesn't care if the wheels are spinning, just as long as they are spinning at the same rate.
Now, in 2wd, or 4hi, both esp and traction control are on all the time. In either of these modes pressing the esp button once will turn off traction control only. You will get a little amber light of a car with squigly lines coming behind the tire. This only disables the part of esp that doesn't want you to spin the tires, but it will still try to keep you on course and from rolling over.
In 4hi, if you step on the clutch or slip it in neutral and hold the esp for several seconds, it will disengage esp and traction control. This means no electronic nannies, just like an old jeep. You will have the amber traction control light on, and also a message in your info center that says ESP off. (We will talk about BLD in just a second.)
In 4lo, there is only one setting, everything off, like the above paragraph, but it does it automatically, and cannot have either traction control or esp turned on.

...BLD's are not as good as lockers! However they greatly expand the capability of jeeps that were not ordered with lockers. IMO, they are better than a plain lsd, although on a wrangler with lsd and bld, it enhances both systems. Now for how they work.

All jeep jk's have an open differential unless the lsd is ordered in which case the rear diff only has the limited slip differential installed, I include jeeps with lockers here since when the lockers are disengaged they function as an open rear end.
In an open diff, both wheels get the same amount of torque from the motor at all times. The problem of this is easily demonstrated in a worse case scenario where one wheel is in the air, and the other is on solid pavement. You would think that since one wheel was on good footing it can pull the jeep right? Wrong. What will happen is that when you give it gas, the wheel in the air will spin and the one on solid ground will do nothing! This is because it may only take 10ft. lb. of torque to turn the wheel in the air since there is no resistance. Both wheels will get 10 lb. of torque, but 10 lbs of torque is not enough to move the wheel with the resistance (solid traction,) so it does not move.

Here is where BLD comes into play. It will apply the brake to the wheel in the air, increasing the amount of torque needed to overcome the resistance. When the torque is high enough, it can and will move the wheel on the ground, both wheels are still getting the same amount of torque, but the brake is creating a need for more torque to turn the wheel in the air, which means the one on the ground gets enough torque to turn it.

Lockers in the JK function just like the described above, until the lockers are engaged. when they do there is a mechanical link between both wheels so that they are physically unable to turn any faster or slower than the other wheel. This is the maximum traction set up.
Back to our example if one wheel is in the air and one on the ground, no problem, if the air wheel spins, so does the one on the ground. This is the best set up for offroad situations, but locked diffs when engaged reduce your turning capabilities and should not be used on pavement.

BLD equipped jeeps can go through many things that the ones with true lockers can, but it is sometimes jerkier, not as smooth, and you have to apply more power, (gas) to overcome the force of the brakes clamping down on the spinning wheel. Lockers are the way to go for ultimate traction, and control.

Next up LSD....I think lsd is the hardest to explain, but to keep it simple, it can by itself without the use of BLD transfer up to 2.7x the amount of torque across the wheels. This means if one wheel has slightly less traction and only needs 20 lbs torque to spin, the lsd can send almost 60 lb. of torque to the other wheel. There is nothing wrong with driving an lsd on the road, it is always active and is better than an open diff for offroad, but not as good as a locker. Why?
Well back to the original example one wheel in the air with zero traction. 10 lb of torque x 2.7 equals about 30 lb of torque, probably not enough to move the wheel.
So if you had a choice, I should think that BLD is a better offroad system than lsd, but jeep one ups me, because the bld is on the lsd too(omg all the acronyms.) It functions the same way, but does not have to intervene as much, and in situations such as dirt or sand where the torque bias is not as high as one wheel in the air, the lsd can transfer torque quicker and smoother across the wheels, but the bld's are stil there to step in if the torque bias is higher than the lsd can overcome and neither the bld or the lsd have to work as hard as they would were it only one or the other. This is a pretty sweet setup.

One more thing, When you're lockers are engaged, there is no need for bld since there is no way for there to be a speed difference across the axle.
BLD is on both the front and rear differentials.

That is the short of it, I know a few more things if you need to know, as well as have plenty of first hand knowledge of these systems.

wow Ben- did you actually write all that?

Nice job!

Here's an example of BLD at work on the front. Watch the drivers side tire- it will spin for a second and then the BLD kicks in giving power to the passenger side (which has traction), and pulls me up




The big key to BLD (and the part that has to be learned for it to be effective) is that the instant you notice a wheel spinning, stay on the throttle but don't hit the throttle harder. Most people react one of two ways when a wheel starts to spin: they either let off the throttle completely, or they slam on the throttle . Both of those are the wrong things to do. Letting off the throttle does nothing (of course). Slamming on the throttle just makes it more difficult for the BLD to brake the spinning wheel, and virtually guarantees that when the BLD does kick in, it will have way too much power- so you'll either break traction with the wheel you're trying to get power too, or you'll have a big lurch forward when the traction side grabs... The key to effective use of the BLD is (when you feel the wheel spin) just stay on the throttle and wait for the BLD to kick in. Once it has kicked in, it may or may not have enough power to pull you. Its at that point that you can actually apply some more throttle- ease into it, don't slam it. Just ease into the throttle until it has just the right amount of torque for the tire to pull you up.

This type of driving does not come naturally. It is something you learn and have to get used to. I got really good at using my BLD. So much so that I debated even bothering with lockers- my BLD's were getting me thru everything effectively enough (I thought). But now I love the lockers. So much easier.

i don't have time to look, but there is a vid out there of a jk with a front wheel in the air and the other on the ground the bld works awesome

I think Maverick has some vids of my bld's working. N2, yes I did write all that. I love mechanical processes and things. Physics has always fascinated me, especially force/leverage/potential/kinetic energy etc. And good addendum to the driving style variation! Here is a link to a vid of my jeep trying to get up a sand hill and some of the commentary that made me want to post the above. (BTW, I wrote that a while back and saved it to my comp so now I can just copy/pasta my epic BLD speech.) Maverick hates it.

https://www.youtube.com/watch?v=_MSGsQpVmnU

Ben wrote:

I think Maverick has some vids of my bld's working. N2, yes I did write all that. I love mechanical processes and things. Physics has always fascinated me, especially force/leverage/potential/kinetic energy etc. And good addendum to the driving style variation! Here is a link to a vid of my jeep trying to get up a sand hill and some of the commentary that made me want to post the above. (BTW, I wrote that a while back and saved it to my comp so now I can just copy/pasta my epic BLD speech.) Maverick hates it.

https://www.youtube.com/watch?v=_MSGsQpVmnU

Click free for ya... Where is that?

Great write up Ben. Thanks for all that info. It answered a lot of questions but got me confused a little, mainly between "traction control" and BLD. From your description, both seem to brake the spinning tire. Is BLD always on, or only in 4Lo or 4Hi /w traction control off? I guess that is where I got confused. I have LSD and no lockers in case that matters.

Was your video in 4Lo or 4Hi? And what a cliff hanger! Is your jeep still there or did she ever get out?

Bizarro wrote:

Great write up Ben. Thanks for all that info. It answered a lot of questions but got me confused a little, mainly between "traction control" and BLD. From your description, both seem to brake the spinning tire. Is BLD always on, or only in 4Lo or 4Hi /w traction control off? I guess that is where I got confused. I have LSD and no lockers in case that matters.

Was your video in 4Lo or 4Hi? And what a cliff hanger! Is your jeep still there or did she ever get out?

BLD is part of the traction control (ESP/BAS) system. But BLD can never be turned off, whereas ESP/BAS can be manually disabled in 2wd and 4hi, and ESP/BAS is automatically disabled in 4lo except the BLD portion.

ESP can get you in trouble in mud or sand- areas where you need to have wheel spin just to keep you going. If the ESP is not disabled in these situations, the computer will sense the wheels spinning and will apply breaks to all of them to stop the spinning. This can bring you to a complete stop. Then you lose all your momentum and get stuck. Basically it looks at the wheel speed of all 4 wheels and looks for a problem, sees a problem, and attempts to correct it by slowing you down. This is good for traction on a wet street, not good for mud or sand.

The BLD however just looks at the 2 wheels on the same axle. And when it senses that one wheel is spinning and the other is not turning, it realizes that the one spinning wheel must have lost all traction and the other wheel must have some traction. So it stops the spinning wheel in order for torque to be sent to the other wheel.

easier way to look at it: ESP want all 4 wheels to spin at the same speed, and the speed needs to be relative to actual speed of the vehicle.

BLD does not care about the wheels spinning, it only cares that the 2 wheels on the same axle are spinning at the same speed.

Bizarro wrote:

Great write up Ben. Thanks for all that info. It answered a lot of questions but got me confused a little, mainly between "traction control" and BLD. From your description, both seem to brake the spinning tire. Is BLD always on, or only in 4Lo or 4Hi /w traction control off? I guess that is where I got confused. I have LSD and no lockers in case that matters.

Was your video in 4Lo or 4Hi? And what a cliff hanger! Is your jeep still there or did she ever get out?

Bizarro, BLD's are always active in 2hi, 4hi and 4lo. The difference between esp, BLD, (and traction control:)

ESP- This is the stability program that tries to keep your jeep from rolling over, sliding sideways etc. It works by sensing that the jeep is going in a direction that is not intended by using sensors to sense the front wheel angle and the path of the jeep. For example if you are making a left hand curve and the rear of the jeep starts to slide out to the right, esp will use the brakes to help correct and get you back to the correct line. This is accomplished by braking the inside brakes of a turn more than the outside making the inside similar to an anchor.

ESP- When ESP tries to prevent a rollover it uses the same sensors but it is measuring pitch angles etc. This time you are in the same left hand corner and instead of the rear sliding out to the right, the jeep starts to tilt to the right and is about to roll. This time ESP locks up the outside tires in order to make them lose traction and slide vs. act as a fulcrum to roll the jeep.

ESP can be disabled in 2hi and 4hi by putting the transmission in neutral or park and holding the esp button for a few seconds. It will automatically re-engage when the vehicle is turned off and then back on or when the button is held again. It is automatically disabled in 4lo.

Traction Control- Doesn't want the wheels to spin. When active and it detects a slip from a tire, it tries to slow that tire down. This can kill you offroad as there are times when you need wheelspin and traction control not only uses the brakes but can cut power (fuel) to the motor to stop the wheel spin. Traction control can be deactivated by pressing the esp button once in either 2hi or 4hi, it is automatically disabled in 4lo.

BLD- Different than traction control in that it doesn't care if the wheels are spinning, just as long as they are spinning the same speed across the axle.

I hope that helps. As for the video... sigh, it was in 4lo and 1st gear and actually floored. I despise the bean counter who thought it was a good idea to put 3.21 gears in a vehicle destined for offroad use. It sucks just as bad on the high way too. You would think that it would give you better fuel economy but in real life it just means you go through your clutch way early, like trying to start out in 3rd gear all the time. It also will not hold 65+mph on the high way because it doesn't have enough leverage to keep the vehicle moving at those speeds. Don't believe it's that bad? I will let you take a drive in my jeep sometime.

Speaking of gears... 3.21's are bad enough but does anyone think that they messed up in the six speed gearing? If it were me and I had a six speed transmission to design and it was for an offroad vehicle, I think I would make at least 1st, probably 1st and 2nd, pretty short gear ratios because you have six gears to spread the ratios. Instead 1st gear feels like 3rd gear in most cars and sixth is basically unuseable unless the wind is behind you.

I now dismount from my soap box.

And sadly, I did not make it up that sand hill.

N2rock wrote:

Bizarro wrote:

Great write up Ben. Thanks for all that info. It answered a lot of questions but got me confused a little, mainly between "traction control" and BLD. From your description, both seem to brake the spinning tire. Is BLD always on, or only in 4Lo or 4Hi /w traction control off? I guess that is where I got confused. I have LSD and no lockers in case that matters.

Was your video in 4Lo or 4Hi? And what a cliff hanger! Is your jeep still there or did she ever get out?

BLD is part of the traction control (ESP/BAS) system. But BLD can never be turned off, whereas ESP/BAS can be manually disabled in 2wd and 4hi, and ESP/BAS is automatically disabled in 4lo except the BLD portion.

ESP can get you in trouble in mud or sand- areas where you need to have wheel spin just to keep you going. If the ESP is not disabled in these situations, the computer will sense the wheels spinning and will apply breaks to all of them to stop the spinning. This can bring you to a complete stop. Then you lose all your momentum and get stuck. Basically it looks at the wheel speed of all 4 wheels and looks for a problem, sees a problem, and attempts to correct it by slowing you down. This is good for traction on a wet street, not good for mud or sand.

The BLD however just looks at the 2 wheels on the same axle. And when it senses that one wheel is spinning and the other is not turning, it realizes that the one spinning wheel must have lost all traction and the other wheel must have some traction. So it stops the spinning wheel in order for torque to be sent to the other wheel.

easier way to look at it: ESP want all 4 wheels to spin at the same speed, and the speed needs to be relative to actual speed of the vehicle.

BLD does not care about the wheels spinning, it only cares that the 2 wheels on the same axle are spinning at the same speed.

You beat me to it barely, I think between our two posts, he should be able to figure it out. (I might have beaten you to it had I not stepped on my soap box.)

Ben wrote:

You beat me to it barely, I think between our two posts, he should be able to figure it out. (I might have beaten you to it had I not stepped on my soap box.)

LOL... Yeah, I guess we're both big fans of BLD.

Go Captain Planet. "By your powers combined!"

Between those two post I now completely understand. Thank you so much.

Ben wrote:

And sadly, I did not make it up that sand hill.

N2rock wrote:

Ben wrote:

You beat me to it barely, I think between our two posts, he should be able to figure it out. (I might have beaten you to it had I not stepped on my soap box.)

LOL... Yeah, I guess we're both big fans of BLD.

from your earlier post N2
that vid is from shiloh ridge....the trip where we saw the land rover and the custom shop from lufkin came out w/the maroon JK

Ben wrote:

Maverick hates it.

l]

At 1st it was interesting but this is how I feel when he starts on his testosterone-fueled BLD sermon

Maverick1701 wrote:

N2rock wrote:

Ben wrote:

You beat me to it barely, I think between our two posts, he should be able to figure it out. (I might have beaten you to it had I not stepped on my soap box.)

LOL... Yeah, I guess we're both big fans of BLD.

from your earlier post N2
that vid is from shiloh ridge....the trip where we saw the land rover and the custom shop from lufkin came out w/the maroon JK

Maverick are you proud of this thread? I'm out spreading the BLD gospel my brother. And speaking of our powers combines, its funny you should mention that, because N2 used to be on that show.

well at least you two don't discriminate- you'll fug up any thread, including your own

I have Eaton E-Lockers front and rear. Should I install BLDs?

And Ben, the ratio spacing on the 6-speed is probably due mostly to the very low (numerically) gear ratio with the tall tires. You move up to, say, 4.56 or 4.88, and you might be annoyed that you don't have a taller 6th gear cruising ratio.

Probably and yes good sir, you should retrofit BLD's. Everyone needs them! In all seriousness what I do like about them is that they give the jeeps that aren't optioned with lockers a lot more capability without adding so much to the cost of the vehicle. In fact i would postulate that it is cheaper for jeep to put bld systems in than it was to put the lsd's in previous gen jeeps.

Ok, I understand. Thanks for the info.





Teacher may I go to the restroom, I need to pee :jk:

BLDS R SRS BUSINESS!!!!

You spam fags stay teh fuck outta my BLD THREAD!

Ben wrote:

You spam fags stay teh fuck outta my BLD THREAD!

*keys up mic*
"Pot to kettle, pot to kettle...come in kettle"

I know your post is old old old. But maybe this will get to you. There are those that say the Rubicon has BLD but does not have LSD, or what ever Jeeps terms are for these. Just verifying as a new 4x4 guy that you say both are active on the Rubicon.....I'm referring to 2012/2013 models. Dealer no help.

Also, in sand, mud, AND rock, do you recommend locking front and rear axles as a precaution? I'm guessing lock ONLY rear if front is having to steer on solid boulder or similar until rear axle catches up..

Finally, in snow, whether loose, packed or icy, isn't 4WH(lockers not possible anyway) the preferred initial setting?

Whew!

ratchettt wrote:

I know your post is old old old. But maybe this will get to you. There are those that say the Rubicon has BLD but does not have LSD, or what ever Jeeps terms are for these. Just verifying as a new 4x4 guy that you say both are active on the Rubicon.....I'm referring to 2012/2013 models. Dealer no help.

Also, in sand, mud, AND rock, do you recommend locking front and rear axles as a precaution? I'm guessing lock ONLY rear if front is having to steer on solid boulder or similar until rear axle catches up..

Finally, in snow, whether loose, packed or icy, isn't 4WH(lockers not possible anyway) the preferred initial setting?

Whew!

wow talk about a blast from the past!!
If ben doesn't reply, Ill give him a call and have him swing in to the forum.

I have had a little time to continue my education on the 4w drive system, and state what I have come up with, no accuracy implied. The overall system is Electromic Brake Control System.......consists of many componets known by acronyms, the principle one is ECS,Electronic Stability Control. The ESC term is misused to describe the whole EBCS(ABS HDC HSA ERM BAS etc) system when it is only a component, the Wrangler Owner Manual being a chief offender.

The parts of interest to me pertain to the Rubicon. I have determined that the Rubi does NOT have mechanical LSD, which is available as an option on Sport S & Sahara. However, all JK's(2012-2013) have TCS, part of EBCS and subsystem of ESC, which(TCS) includes a "limited slip LIKE" system, I believe this is the electronic BLD refered to in this thread. If this is untrue, towel is going into the ring and I'm done.

Furthermore, the BLD is active in all ESC settings(on-off-partial off) except on the Rubi WHEN lockers are engaged. Unclear if the BLD still operational on front axle if it is unlocked with rear locked. When ESC is partial off, the aspects that brake the vehicle and regulate power to slow it are disabled allowing wheel spin in mud/sand, but BLD is still active to control and synch speed of spin on same axle wheels. Certain subsystems of EBCS/ESC are still active(not sure which ABS? ERM? BAS? etc). In FULL OFF only the portion of TCS that equalizes the speed of wheel spin is active and that's our electronic BLD. Again, if not the towel goes in.

So thats where my digging took me. No dealer or any one at Jeep I know knows, but many are happy to give bad information and add to the myths and folk lore of THE JEEP.

Any feed-back?

Ok, you're close,

BLD is on all axles of all jk jeeps, (front and rear.) It is part of the electronic suite that controls ABS, TCS, and ESC, but it is a separate program. In other words, BLD's work to keep both wheels turning at the same rate regardless of wheel speed or vehicle trajectory. TCS doesn't want any wheel spin and that is one reason it is turned off in 4lo automatically. Ditto for ESC except ESC is more concerned with keeping the vehicle from sliding laterally or sideways. when you are in 4hi by default both esc and tcs are still active. You can disable TCS by pressing the traction control button once, esc and TCS by being completely stopped and holding the traction button for a few seconds till a beep goes off and you see the indicators on the dash go off. At this point in your rubicon you are in 4hi with no electronic nannies assisting traction other than bld's. BLD's will never be shut off.

You say that the BLD system is deactivated when you are in 4lo and lock your front or rear axles, but that's a little misleading. The system is still functioning but if the axle is locked there is nothing for the system to do since a mechanical lock between the axles doesn't allow one wheel to spin faster.

If in your Rubi you were in 4lo and had just the rear diff locked, the BLD's would still be active on your front diff even though the rear is locked.

There is no mechanical limited slip device in a rubi. On the saharas or sports that have an LSD installed, this just further enhances the BLD system as its work load is lighter. Remember a LSD with no BLD will spin a tire if one is in the air and another on the ground. BLD is able to overcome that torque bias and turn the wheel on the ground. If there is an LSD added to the equation the BLD's will still be able to turn the wheel on the ground but won't have to work as hard. I have never been wheeling with a JK with LSD but I would imagine the torque transfer would be a lot quicker in loose sand and mud.

I hope this helps. All my information is from me and Maverick's studies as well as personal experience and firsthand knowledge. Let me know if there's anything else you're confused about or need advice on. I can also give you way more info than u might ever need concerning water crossings and the weak points on a jk.

Ben