How well does BLD (brake lock differential) really work?

myerides

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When locating my Sport S we couldn't find the "perfect combo". So when I realized that I was going to have to sacrifice one option I chose to forego the "anti-spin" (limited slip) diff. I figured I would add a locker later and I probably will. It wasn't until last weekend that I knew BLD (Brake Lock Diff) was a thing and that all new Jeeps have it. I've read a few articles on it that make it sound like a pretty good alternative to get me by until I add the locker. So I'm curious to hear from anyone that has actually had their open diff JL on the trails and/or rocks and can give me first had feedback on how well it performed.

Thanks!
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The_Phew

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Every passenger vehicle sold in the U.S. in the past decade has traction control; BLD is just FCA's marketing name for theirs. Obviously different manufacturers/vehicles have different programming, but the end result is always similar. The JL uses different parameters for 2H, 4H, and 4L, so that makes it a bit more special than traction control in a Corolla or something, but it's no groundbreaking tech.

It works, but in principle I'm against the application of brakes to aid in acceleration. On ice/snow/sand/mud/etc I prefer a mechanical LSD, or better yet, an electromechanical LSD (not available on the Wrangler).
 

bobzdar

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Every passenger vehicle sold in the U.S. in the past decade has traction control; BLD is just FCA's marketing name for theirs. Obviously different manufacturers/vehicles have different programming, but the end result is always similar. The JL uses different parameters for 2H, 4H, and 4L, so that makes it a bit more special than traction control in a Corolla or something, but it's no groundbreaking tech.

It works, but in principle I'm against the application of brakes to aid in acceleration. On ice/snow/sand/mud/etc I prefer a mechanical LSD, or better yet, an electromechanical LSD (not available on the Wrangler).
It is not traction control in that it does not cut engine power to prevent spin, which is what the normal traction control system (and most normal traction control systems) do. It just applies brake to the spinning wheel and routes the engine power to the other wheel without cutting engine power. Some cars can have their traction control system put on a special mode that makes it a bld - in BMW you hold the traction control button down until it blinks and it goes into 'performance' mode which is bld. So it's definitely not normal traction control.

It does 90% of what limited slip or lockers do, but it's not as smooth and can overheat the brakes if used constantly (like say doing the rubicon trail), so lockers still are definitely the way to go if you do a lot of serious off road, but for the occasional off road jaunt that has a handful of really rough obstacles, the bld is perfect.
 

Patinito

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In a situation where you would go mudding and assuming you have LSD in the rear, would it be best to turn off traction control/BLD? Would BLD be best used on the road and rock crawling and turning it off for mudding and sand?
 

D60

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Nah, modern traction control can also get kinda muddied with yaw control but now most systems cut power AND apply brakes to various wheels as needed.

Subaru was all happy on their marketing of "transferring power from the wheels that slip to the wheels that grip."

Ultimately I agree that braking a spinning wheel to force power to the one with traction is.... questionable. If it works, it works but a system that actively propels both axleshafts is superior.

For one thing in order to have a BLD that really works great it would have to be programmed aggressively and would be anything but transparent. Now I haven't used FCA's so maybe it's great, I dunno.

If you're on Moab slickrock how does it know when that airborne wheel (which should have the caliper locked up) touches down again? 'Cause if it doesn't release immediately it's only gonna hinder forward progress....
 

Patinito

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If you're on Moab slickrock how does it know when that airborne wheel (which should have the caliper locked up) touches down again? 'Cause if it doesn't release immediately it's only gonna hinder forward progress....
Good question. I've seen that even though the tire is locked up it still jerks about in the spin, possibly to "sense" when it gains traction again. Maybe when it hits the ground and totally stops spinning and gains traction is when it disengages BLD.
 

D60

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As linked in the other thread if you watch this all the way through the middle vehicle with traction control appears to essentially be using a BLD when it lifts tires. It may also be throttling power, hard to know.

It *does* get him through much better than an open diff
 

D60

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Patinito, you're absolutely right, it's the only thing that makes sense. It's constantly unlocking and checking that WSS to see if it matches the other. If it continues to overspeed the opposite side it locks again, rinse and repeat...
 

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Traction control system is designed for safety, it cuts power and/or applies brakes to avoid a spin out. It will activate if wheel spin is detected, side to side or forward speed vs wheel speed. BLD is ON even after you turn traction control off and it's purpose it to get you unstuck. It does not cut power and it does not get activated for forward speed vs wheel speed difference, only for side to side spin. They both use the same hardware but traction control in most cars will only get you stuck not the other way around. In Jeep's(atleast in the Grand Cherokee) they work reasonably well but you need to keep giving it some gas for a while after you are stuck.
 

boon4376

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The 2012+ JK's (newer drivetrain) have great BLD's. I had it in my 2013 JKU and it was very rare I couldn't get to where the guys with lockers were going.

You have to spend more time picking your line, tire choice is more important, as is suspension flex (disconnecting your front sway bar to keep both front wheels on the ground helps a lot too).

That said, a real locker will always have more traction without needing to wait for wheel slip... But those situations are rare, and just require some finesse and skill on part of the driver. Real lockers also need more caution because if you have too much traction, you'll put a lot of excess strain on your drivetrain (ujoints, gears, shafts, etc.), and eventually you'll start breaking things. (you should really only lock when you need to be locked, and stay unlocked at all other times).

You have to have trust that the BLD's will kick in and help you crawl through - I see many people stop way to early when they should have stayed on the throttle and let the BLD's work it out.
 

COSJL

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In a situation where you would go mudding and assuming you have LSD in the rear, would it be best to turn off traction control/BLD? Would BLD be best used on the road and rock crawling and turning it off for mudding and sand?
You definitely should turn off traction control in both cases. However, BLD is always ON on all open diff axles even if you turn traction control off. I know engaging lockers turn BLD off.I would think BLD would be off with LSD, but not sure.
 

D60

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You definitely should turn off traction control in both cases. However, BLD is always ON on all open diff axles even if you turn traction control off. I know engaging lockers turn BLD off.I would think BLD would be off with LSD, but not sure.
I would think a limited grip would work in tandem w BLD quite well. It will theoretically require less braking force to send power to the wheel with traction. OTOH too much brake might burn up clutch packs sooner, maybe??
 

JLUin818

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With the anti-slip package you also get a D44 rear end. Its a heck of a deal for the package
-lsd
-d44
-all terrain tires
 

Renegade

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My opinion in simplistic terms:
  1. BLD is better than either locker or LSD in snow and on ice
  2. BLD is almost as good as locker, and equal to LSD in mud
  3. BLD is not as good as LSD or locker in rocks
 
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