The JK's Brake Operated Limited Slip

[Hilldweller]

HI Hill,
Yes, the obstacle was difficult but you did make it. Actually, pretty impressive performance.

Sparky

Frustrating really.
It was just a little wheelspin but it was all 4 wheels... ...the one thing that BLDs don't know what to do with. Stopped me dead each time until I got half a tire in the little gap a the top.

That's a nasty steep park though. I only had one other time that the BLDs slowed me down and I beat that by airing-down more.

But lockers win...

 

[jdzl]

Frustrating really.
It was just a little wheelspin but it was all 4 wheels... ...the one thing that BLDs don't know what to do with. Stopped me dead each time until I got half a tire in the little gap a the top.

That's a nasty steep park though. I only had one other time that the BLDs slowed me down and I beat that by airing-down more.

But lockers win...

I know it probably makes no difference - but just to satisfy my curiosity... Are you running an auto or manual transmission? Was the ESP/BLD literally just bogging you down to a stop? Was that in 4-Low? (Not trying to insinuate you did something wrong, just trying to figure out what circumstances will cause this so I'll know when to expect it)

 

[Hilldweller]

I know it probably makes no difference - but just to satisfy my curiosity... Are you running an auto or manual transmission? Was the ESP/BLD literally just bogging you down to a stop? Was that in 4-Low? (Not trying to insinuate you did something wrong, just trying to figure out what circumstances will cause this so I'll know when to expect it)

4-low, autotrans, 20 psi in MTR-Ks. You could feel the BLDs grab ---- which is a welcome feeling when you want it to happen...
Then it would just sit there and shake in a sad spastic way.

Momentum killer.
Like I said, it happened one other time. New Years run on a half frozen/half muddy hill. Very slick and lots of fails that day. I tried it 8 times and failed 7 of them like in the video --- just a sad spastic shudder. Then I aired-down more and got better traction and went right up.

Here's the run that was successful. The BLDs are kicking-in when appropriate and helping.

 

[jdzl]

Looks like you got a decent amount of wheelspin in the front on that aired down run, so they must have been going the same speed (side to side) for the BLD not to "help" I guess?

When it stopped with the shudder did it feel like something that you could've overcome with more throttle or was it like someone was standing on the brakes?

 

[Hilldweller]

When it stopped with the shudder did it feel like something that you could've overcome with more throttle or was it like someone was standing on the brakes?

From experience I know that a little more speed, momentum, would've done the trick. But I wasn't willing to go any faster on that hill. I had already done a couple of front-end air sessions that morning on the hills of Beasley; it was wet earlier and that's a really entertaining situation in that park...
From the seat-of-the-pants, yes, it felt like a divine entity was standing on the brakes. Sorta like in Star Wars when Obi-Wan powered-down the forcefield of the Death Star --- that noise it made... ...and all of a sudden, nothing. Why'd I stop? There's no stop sign... ...I didn't hit the brakes... ...how do I turn this off?

 

[JCMatthews]

A few years back, I spoke with AEV engineers at EJS in Moab. They were running the last gen. Grand Cherokee with the Super Lift 4.5 inch lift. We asked them how the vehicle performed off road and they told us it was so amazing that they never even engaged their lockers. The brake lock differentials made all the difference. My father has them in his '12 grand and my brothers have them in their '05 Commander and '12 Rubicon. (wish they were in my '05 Tundra) They have never slowed them down, just kept them moving forward. I used to have a Cherokee that was locked in the rear, and there are some hills (usually loose dirt) where I would lose traction and just spin. I can also tell you from experience as a trail guide for the Red Rock 4Wheelers EJS event, that you are not airing down enough if you are only running 20 psi. In my Cherokee, I would run 33X10.5
BFG ATs at 8 psi. I did not have bead locks and it was never a problem. I really out performed many others and they were always amazed. it took me years to be brave enough to run it that low. I started out at 20 and then 18 , then 15, 12, 10 and finally 8. I had one close call, but the tire always stayed on the bead. I believe from what you have said that you have figured out that when you have less air in your tires that your Jeep has better traction. BLDs will not make up for over inflated tires.

 

[HillbillyfromAL]

If your Tundra has traction control its the same basic idea. Interesting to see that Jeep is finally starting to use it though. Traction Control is where Land Rover has it down right. My 2004 Disco performs better than my old 04Rubicon on about 90% of stuff. The only thing the Rubicon would do better is the more Extreme stuff where lockers Are really the only way to go. TC is way better on the ice and snow too. The one thing is TC/BLD or whatever else someone decides to call it works best with slow steady throttle and you letting it do the work. The problem lies in that it's a reactive system so that jarring/bouncing is alot of times caused by the system, where with lockers that same feeling is what comes before your going to break something. It took me awhile to get used to it and stop letting off the gas which from those videos seems like what was happening. It'd be interesting to see a side by side comparison of the different TC systems and the same Jeeps with lockers.

 

[Hilldweller]

No; 20 psi was not low enough.
15 psi finally became the sweet-spot for those tires and then the Coopers. Airing-down values depend on tire brand, rating, weight of vehicle, terrain...

 

[JCMatthews]

Sounds like you're getting the psi required for your type of terrain figured out. I bet when you do you won't get stopped any more.

 

[HillbillyfromAL]

Hilldewller you ever been up Mt.Yonah? I used to be stationed at 5th RTB man I miss that place.

 

[Awkragt]

I'd say bld works really well. It's fun to watch it work on loose ground. A little wheel spin and kicking up rocks is sometimes funnier than hitting the easy buttons and just driving up something.

Have driven in deep snow, Moab, mud, the lockers came in handy on only the craziest stuff. Even then, a few more attempts and the BLD would've got me there. Bld is definitely harder on driveline components because of the jerking it creates. Bld has to be used with plenty of momentum.

A buddy of mine had a tj with limited slip and the bld on the jk was way better. The limited slip is kinda an on road at speed traction control. Not slow rocks, deep snow, and flexed out stuff. The bld works surprisingly well when a tire is off the ground.

I'd go plain bld for a while then lockers well down the road.

 

[4X4NDAD]

Being a Toyota Tech I've been able to get used to the Fj A Trac system, before getting my Jk. Here's the secret. EBDS, lockers, limited slips, carpets , chains, floor mats, are all traction aiding tools. It doesn't matter which way you go or how much you spend as long as which ever method you choose works at 1am. And you have to work in the morning. Ebds works but it has its limits. For overland use it's a perfect medium, the important thing is to learn how to drive with it.

 

[RubiconGeoff]

I have a 2010 Rubicon and so have direct comparisons between the BLD and lockers at the flip of the switch (since the Rubicon's axles have BLD as well as lockers.) The system works and it beats the hell out of lockers around town in the snow, except for deep snow. In fact BLD is better than lockers most of the time in snow where you need to do any amount of turning or when you're off camber. BLD is helpful everywhere off road but doesn't compare to lockers. When you need lockers you need lockers. BLD works in 4 hi too, as opposed to the oem locker set up.

I've had a chance to play around in a variety of snow conditions with my 2010 Rubicon and I 2nd what JPK has said here. I would prefer the BLD (Brake Lock Differential) to be called BLS (Brake Limited Slip) to better describe its operation.

As long as you have momentum, the BLD works great! I am genuinely impressed with how well it works for its intended purpose. However, it does have its limitations and it's not a substitute for a pair of proper locking differentials. For example, I was traveling up a steep unplowed road in which the BLD was obviously and effectively managing wheelspin and torque distribution to ensure all 4 wheels were pulling. As I got higher and higher up the mountain, the snow was getting deeper and the slope was getting steeper. In the tougher sections, I could really feel the brakes bogging down the engine just as I was needing more wheelspin, not less. Eventually, at this steep section the BLD killed all forward momentum as it stalled the engine (manual transmission, high range):



BLD prevented any further forward progress. In terrain like this, there is no substitute for true diff locks. I engaged both lockers and drive right out of this.

 

[williard86]

I read a great article explaining the difference between the different systems--open difs, bld, limited slip, and lockers. Wish I could find it because I don't remember specifics. The article put the different systems in the same set of scenarios and explained how each managed the torque. I'll keep looking.