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- redneck
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- 88 5.0 LX, 08 F-150 Stepside, 22 Expl Timberline
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The parking brake doesn't rely on the hydraulic system at all. Here's a picture of a rear caliper from a car with an electronic parking brake:
See that splined shaft? That's where the parking brake actuator engages and directly drives the piston. So you could have a busted line or no brake fluid or anything, and the actuator would still be able to apply rear brake pressure.
4H: The front and rear axles are locked together by the transfer case. Depending on whether or not the front and rear diffs are also locked, all four wheels could be 100% mechanically locked together. Great for crawling up rock walls or powering through mud or sand. It is NOT intended to be used on a paved surface with high traction. It causes chattering and wheel hop when turning as the tires actually need to rotate at different speeds when making turns, but they can't because they're all locked together.
4A: The transfer case modulates lockup between the front and rear diff, transferring power to where it detects traction.
If you're driving on the road in bad weather with intermittent slick patches, 4A is 100% preferable. You don't want all four wheels locked together when you have good traction. You want the system to send power to wherever it can find traction.
And if you pull away from a slick stop in 4H with everything locked together, all four wheels will spin, allowing the vehicle to drift side to side. 4A would take power away from the spinning wheels and give it to the ones with traction, improving acceleration and maintaining control.
People get all sorts of bent out of shape about the above. "I've been driving with 4x4 in the snow for years! Just turn it off if you don't need it! If you can't get around in the snow in 2wd you're just a dummy and a bad driver!"
I'm not saying it's impossible to get around in 4x4 or 2wd, I'm saying the optimal configuration for maximum control and acceleration in slick conditions is one that can actively choose where to send power. The Wrangler finally got 4A with the JL, before that I couldn't understand why people bought a Wrangler as a winter vehicle. Without 4A, you're just running around in 2H all winter except the few mornings when you beat the plows to the roads.
But 4H and locking diffs is 100% optimal for mud, sand, or rocks.
Thanks Laminar, lots of good info there. I am VERY aware of lockers and what they can and what you shouldn't do. I take my son four wheeling all the time. Mine is a 98 600 Grizzly and his is an 08 350 Grizzly with front locker, mine is the older model without locker. If you don't ride a wheeler give it a try with the locker on all the time, it will wear you out in a hurry, it's a lot harder to steer. So when I am talking about driving in 4WD on the roads that is WITHOUT lockers even if I did have an electric locker I wouldn't have it on because as long as one front and one rear tire is pulling it will 9 times 'outta 10 keep you out of the ditch. You only need the locker when the shit hits the fan, so to speak. IMO. Come up on a situation while off-roading and simple switch the locker or lockers on, when through switch them off. Personally I love the 4WD drift in the snow, its almost as much fun as drifting my fox body on the freeway on ramp switch back !!
So since we are on the subject of how things work, how about some thoughts on how to use the "front dig". Keep in mind I don't think it will be like Toyota and just turn the wheel to lock and the ECM does the rest. The Bronco has a lot of excellent features and I don't see Ford doing it this way. I think it will be more like a "combo" like described above. I was thinking 2H and front locker on and the ECM would just "switch" the case to front drive But from what you have just described and what others have said about 4A, my new guess would be 4A, so the ECM could just transfer all the power to go to the front. …….. but I also noticed a button on the dash pod, on certain models, has what appears to be a transfer case lock ???? Could the transfer case lock be there so in 4A you can "lock" transfer case so it splits the power 50/50 ??? But then what is the point to 4H ??? This reveal may leave me with more questions than answers.
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