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Unread 12-31-2011, 03:16 PM   #1
meopilite
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use brakes to help gain traction?

I've heard that with open differentials, you can moderatly apply the brakes to help stop the spinning wheel and regain torque to the other wheel.

Has anyone tried this?

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Unread 12-31-2011, 03:49 PM   #2
jeepyj13
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Yes ive tried and i failed. Maybe someone else will chime in on this
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Unread 12-31-2011, 04:09 PM   #3
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The military actually teaches a class in how to do this. I heard it works really really well but its hard to learn to do
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Unread 12-31-2011, 05:02 PM   #4
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With the LSD in my rear axle it helped, although these days I think my clutch packs are pretty worn so more like an open rear. Worth learning to do, although no substitute for an actual locker.
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Unread 12-31-2011, 05:57 PM   #5
DanZ51
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Originally Posted by Siva283 View Post
The military actually teaches a class in how to do this. I heard it works really really well but its hard to learn to do
That instruction is part of HMMWV operators' training. It's effective with the TORSEN torque biasing differential. It is not taught AFAIK for any other vehicle (air brakes and throttle is not a healthy mix).

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Unread 01-01-2012, 05:05 AM   #6
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JK's have a system that does this automatically and it does a great job getting a rig with open axles over stuff you would not think possible. Trying to do this manually with a brake pedal won't be nearly as effective.

Get lockers.
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Unread 01-01-2012, 12:49 PM   #7
wendell
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It works, but it even works better with a detroit tru-trac. With some brake, it will force both wheels to turn together like a locker. The TT sends power to both wheels, but more to the wheel with the most traction. A little brake presure makes the TT send power to both wheels in an allmost 50/50 split. I run the TT in both ends of my yj so I can have good highway manors and with a little brake, locker like traction if I get a wheel lifted off road.
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Unread 01-01-2012, 03:16 PM   #8
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Yes, it works really good with Tru-Tracs. In fact, I'm running a Tru-Trac in my front axle right now and as you can see numerous times in the following video you would be hard pressed to tell the difference from a locker:

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Unread 03-13-2013, 09:49 PM   #9
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Old thread but I had a thought.

On the line of using the brake to produce torque as get unstuck, what is the effect of a locker on the rear on the front wheels? My thinking is that if tires get stuck due to lack of torque and the locker splits torque won't the spilt more torque to the front as well since the transfer case is locked?
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Unread 03-14-2013, 01:17 AM   #10
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Originally Posted by No4x4Yet View Post
Old thread but I had a thought.

On the line of using the brake to produce torque as get unstuck, what is the effect of a locker on the rear on the front wheels? My thinking is that if tires get stuck due to lack of torque and the locker splits torque won't the spilt more torque to the front as well since the transfer case is locked?
Torque split in the t-case depends on the type of t-case. The NP231 splits torque 50/50 to front/rear.
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Unread 03-14-2013, 07:57 AM   #11
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Originally Posted by NonRubicon View Post
Torque split in the t-case depends on the type of t-case. The NP231 splits torque 50/50 to front/rear.
Right. So with open diffs, with tires spinning front and rear there would be near 0 torque. Adding a locker in the rear, the tire with traction now demands torque, say 50 ftlbs. The engine would have to produce 100 ftlbs, sending half "50%" to the rear and the other 50% to the front now correct?
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Unread 03-14-2013, 01:12 PM   #12
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The t-case can send the potential energy (in the form of a spinning shaft) to produce the torque. The t-case in the NP231 splits this potential energy equally, and you can see this by observing how the front and rear axles spin at the same rate in 4WD. This potential energy is not the same as actual torque though - the tires must meet with resistance for torque to actually be produced. If there is no load demand/resistance at the tires, there is no torque. Potential energy is just that - potential. It can be all show and no go without the traction that allows the torque to be produced at the wheel. At best under optimal traction conditions, the t-case can split torque 50/50 to front and rear.

If you had a locked front wheel that required 50 ftlbs to move it forward, and the locked rear required 50 ftlbs to move it forward, then the engine would need to produce 100 ftlbs to split between the front and rear. This is an ideal traction situation.
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Unread 03-14-2013, 01:48 PM   #13
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Originally Posted by NonRubicon View Post
The t-case can send the potential energy (in the form of a spinning shaft) to produce the torque. The t-case in the NP231 splits this potential energy equally, and you can see this by observing how the front and rear axles spin at the same rate in 4WD. This potential energy is not the same as actual torque though - the tires must meet with resistance for torque to actually be produced. If there is no load demand/resistance at the tires, there is no torque. Potential energy is just that - potential. It can be all show and no go without the traction that allows the torque to be produced at the wheel. At best under optimal traction conditions, the t-case can split torque 50/50 to front and rear.

If you had a locked front wheel that required 50 ftlbs to move it forward, and the locked rear required 50 ftlbs to move it forward, then the engine would need to produce 100 ftlbs to split between the front and rear. This is an ideal traction situation.
When your saying locked wheel your meaning stuck? I think were saying the same thing but not sure. My thinking is that if the right wheels are stuck and lets say require 50 ftlbs each to move for simplicity and the left are on ice. Now say for arguments sake you could just put a locker in on trail instantly A locker in the rear would allow the engine to make 50ftlbs for the rear and 50 for the front, goin to both front wheels throw the open diff. Now both stuck wheels in theory would drive themselves out under power.

I tried having this discussion on the Cherokeeforum and those guys are like lil kids. Will it work? NO. Why wont it work? NO!!
If you care to read.
http://www.cherokeeforum.com/f67/poo...-break-164772/
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Unread 03-15-2013, 12:17 AM   #14
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I think I went a little physics oriented - doesn't always translate well. Let me try again.

For starters ignore the t-case split. The differential is the important feature here for your scenario of open front diff and locker in rear.

The core of the open differential is the spider gear. This allows one tire (axle half) to turn at a different rate than the other. It does this by essentially pivoting the left and right axles off each other. Left axle is the pivot for the right, and right axle for the left. If the left tire is spinning free, the right side gets no power. The stationary tire (stationary = not turning) in your scenario cannot drive the vehicle until the other tire gains traction, but the other tire cannot gain traction because it is spinning free on ice. Thus you are stuck going nowhere because the differential is sending the all that drive line power (the potential torque) to the wheel that has no traction. Thus the front axle cannot pull the vehicle forward.

So, in your scenario, the open differential front axle does nothing for the forward movement of a vehicle so long as one tire spins freely without resistance. Both tires need traction (or resistance by means of applying the brakes). The vehicle only moves forward in your scenario due to the rear right tire, on the locked axle, having traction. This forward motion has no impact on the open diff in the front axle gaining traction.

If the front axle had a locker, the front right and rear right tires (the ones with traction) in your scenario would get the torque split from the t-case.
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Unread 03-18-2013, 04:09 PM   #15
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I think your just taking about the axle/differential while im trying to look at it as a whole. As you said each axle "pivots" off itself but you cant leave out the driveshaft cuz that is connected to the spiders gears as well. The driveshaft provides torque from the engine but if there is traction the engine doesnt build torque to spin the tire with grip. A good analogy for the torque thing is trying to loosen a lug nut thats on a car thats already jacked up. Your fully capable of producing the torque to loosen the lugs but with out opposing friction the tire just spins so you arent making any more torque than is required to spin it. To get into physics a lil Power in must equal power out.

To go back to my example. Right twos wheels front and rear have traction but not enough torque to spin them with the opposing wheels spinning front and rear. The engine has nothing to pivot against and make any torque. The required 50 ftlbs to move isnt there. If you put a locker in the rear the engine will now be able to produce the necessary torque. Still with me? The rear axle only get half of the torque though, so the engine is producing 100ftlbs. since there is a 50/50 split front to rear the front gets 50 ftlbs as well. Since open differentials spilt torque evenly the front can apply the same equal 50 ftlbs left and right that the rear can.
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