BLD is basically a traction control function.
What it does is attempt to keep both tires on the same axle spinning at the same speed. Easy way to show how it works is find a V-ditch and get two wheels with no traction and watch it engage and pull you out. If you had only open diffs, you would be stuck. No, it is not like a true locker, but it is better then open diffs. It works better at lower speeds also.

http://blog.chryslerllc.com/blog.do?p=entry&id=270

 

I going wheeling with other JKs and watch what is happening... here are my observations.

When you are at a stand still, it will take 2 or 3 seconds for the system to react and shift power to the wheel that is not spinning. When the wheel on the ground begins to move, it moves slower. It also takes more torque to move up a ledge. But it does work! The tire will turn and the jeep does climb up the legde. it's pretty cool to watch and when I point it out to others, they thinks its cool. Typically you hear comments like... $hit, its amazing what computers do these days.

If you are spinning, it will oscilate the rate of tire spin from one wheel to the next. Tire spin is noticably slower for the tire with the most traction... impact, when climbing up a wet hill, its not as effective... better than nothing at all, but not as effective as both tires turning at same rate.

Works great with limited slip as previously stated.

 

so essentially, without the LSD, the brake lock diff simply does not exist. This is what I seem to be hearing. Therefore the manual application of brakes is pointless and will simply cause cause excessive wear to these parts

 

The BLD is independent of whether you have LSD. It is related to the ABS system. Simply put, it applies the brakes to a spinning wheel in an attempt to transfer power to the non-moving wheel. In some situations it works well and in others it's not so great.

 

It is certainly no replacement for lockers, but it can be effective in some situations. It is the only part of the ESP function that remains active in 4 low. As mentioned, when a wheel loses traction, the ABS system applies braking to that wheel, which eventually exceeds the threshold allowing traction to be applied to the other wheel that has traction, and it does take some time for this system to work.

 

From what I read, he's wondering about trying to get a posi-effect in an open differential using the brakes.

Im my experience (with an S10 that would get stuck in wet grass going downhill) and other 2wd trucks with an open rear:

There is somewhat of a posi-track effect you can somewhat get out of an open-diff. When an open diff slips, one tire unloads all the power goes to nothing. Applying the brakes slightly helps somewhat to try and 'even' the load between the two wheels. Using the brake with the gas can help you get out of 'a little stuck'.....but really wont do squat if you are really stuck.
There really is no replacement for a posi locker unit though.

 

ya that's what I was wondering. I'm very well aware that I'm not expecting locker like effects (that would be too much to ask for!) But if I could get some extra benefit then I won't feel too bad getting aussie lockers up front for now and waiting for Aussie to get something together for the rear.

 

The BLD sucks in sand. When you start to bog down and give it the gas it starts to hit the brake on the wheel that is slipping more than the other one. Then the jeep starts to shake like crazy and you can see a washboard effect if you look at your tracks behind you. Every time it happened to me I just lifted, and hit the clutch as I did not want to break anything. Then you are stuck, and have to back up and start again.

If I could use the lockers in high this wouldn't happen cause you can't use low in sand with a 4:1 transfer ratio. Speed or momentum is the ticket to success.

Bottom line BLD is not what it is made out to be by the sales mumbo jumbo.

Don

 

I must be missing something. According to the owner's manual, the Jeep's computer handles brake lock diff automatically. Mine works, I've seen it first hand.

 

If that's the case then it has nothing to do with the BLD function listed in the ops original post. I've seen a couple clicks on the emergency brake used before as well, but its nothing I would put to much faith in.