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  #25  
Old 09-19-2012, 10:28 AM
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Why does Jeep advertise open diffs as a 'brake lock differential' ? Tell me if I'm wrong but isn't it still a normal open diff with help from brake traction control?
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  #26  
Old 09-19-2012, 10:37 AM
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Re: Quadra Drive II vs. Quadra Trac II

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Originally Posted by Schweibs View Post
Why does Jeep advertise open diffs as a 'brake lock differential' ? Tell me if I'm wrong but isn't it still a normal open diff with help from brake traction control?
That seems to be a convention in the industry, not only Jeep. They view is as brake traction assisting the differential.. locking one wheel so the dif can provide power to the other... so the term gets turned on it ear.

All WK2s have brake traction control on the front axle. All WK2s with the exception of QD have BTC on the rear. QD uses a limited slip Differential on the rear and no BTC.

ESC (electronic stability control) operates on each wheel regardless and in conjunction with the ABS and brake traction.
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  #27  
Old 09-19-2012, 10:42 AM
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Originally Posted by ColdCase View Post
That seems to be a convention in the industry, not only Jeep.
It's almost annoying to me that the industry is doing this..

Oh and thanks for the explanation ColdCase
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  #28  
Old 09-19-2012, 09:43 PM
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Re: Quadra Drive II vs. Quadra Trac II

Thanks for all the explanations.

As I see it with my jeep without qdII, I can lock the center diff only by going to 4lo.. This is probably fine for what I do, but I do sort of wish I could lock it separate from 4lo. I would think that would obviate the need for a elsd in snow conditions for the most part.

I can understand the marketing of the ELSD and "electronic locking diff" being actually just brake assist. Actually, it's ingenious. But It's hard to get the true info on the mechanics of these vehicles sometimes. And the more you know how your car works, the more you can work your car. This isn't just talk either. I've seen pretty expensive AWD vehicles sliding backwards down hills where I live - mainly from TC being overzealous I think.

Thanks again. Good thread.
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Old 09-20-2012, 12:05 AM
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Re: Quadra Drive II vs. Quadra Trac II

Driver skill and tires can make a big difference.
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  #30  
Old 09-20-2012, 04:23 AM
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Re: Quadra Drive II vs. Quadra Trac II

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Originally Posted by comnjeep View Post
As I see it with my jeep without qdII, I can lock the center diff only by going to 4lo.. This is probably fine for what I do, but I do sort of wish I could lock it separate from 4lo.
I've often wished that too - a locked 4Hi mode (the mitsubishi 4x4 have this).

However, the reason they don't is that the centre diff is also effectively an ELSD (also made by Eaton I think). This means that it can also lock (partially or fully) automagically as conditions require, much like the rear ELSD on QD2 will lock as required (and it does NOT use brakes to do it).
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Old 09-20-2012, 10:40 AM
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Re: Quadra Drive II vs. Quadra Trac II

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Originally Posted by Brett View Post
I've often wished that too - a locked 4Hi mode (the mitsubishi 4x4 have this).

However, the reason they don't is that the centre diff is also effectively an ELSD (also made by Eaton I think). This means that it can also lock (partially or fully) automagically as conditions require, much like the rear ELSD on QD2 will lock as required (and it does NOT use brakes to do it).
A locked center dif in 4Hi would be more likely to cause dangerous binding and damage to the vehicle or loss of control. If people could go 45 or 55 MPH in 4Hi and locked center diff, and this would be far more likely to cause damage...probably also really screws with the stability control programs that kick in at those speeds.

I think you have no business locking a center differential at speeds higher than 25 mph.
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Old 09-20-2012, 11:22 PM
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Re: Quadra Drive II vs. Quadra Trac II

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Originally Posted by Trailpixie View Post
A locked center dif in 4Hi would be more likely to cause dangerous binding and damage to the vehicle or loss of control. If people could go 45 or 55 MPH in 4Hi and locked center diff, and this would be far more likely to cause damage...probably also really screws with the stability control programs that kick in at those speeds.

I think you have no business locking a center differential at speeds higher than 25 mph.
I totally agree with you there Trailpixie.
The reason I would like to a locked 4hi is because I drive on a lot of soft sand tracks where the speed is always less than 25mph, but the Jeep has plenty of torque/capability that 4lo is overkill most of the time.
I guess it's a confidence issue for me - I need to trust the limited slip nature of the centre diff - I'm just note sure how quick it is to react?
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Old 09-21-2012, 07:02 AM
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Re: Quadra Drive II vs. Quadra Trac II

Quote:
Originally Posted by Trailpixie View Post
A locked center dif in 4Hi would be more likely to cause dangerous binding and damage to the vehicle or loss of control. If people could go 45 or 55 MPH in 4Hi and locked center diff, and this would be far more likely to cause damage...probably also really screws with the stability control programs that kick in at those speeds.

I think you have no business locking a center differential at speeds higher than 25 mph.
On my pickup trucks and WJ I've used 4WD lock all the time in winter conditions where you can go from dry roads to snow covered in an instant and back again. You often come up on a slush mound and need the 4 lock to pull you through. I have never had an issue with binding or stability at highway speeds (~75). At the parking lot or turns at an intersection I slip it out of lock. Makes for a much safer ride if you have to be out in those conditions and have a long way to go. Ever since shift on the fly was introduced, the transfer cases have been designed for 4 lock at highway. It does kill MPG and put added wear and tear on the driveline, so I wouldn't recommend setting and forgetting.
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  #34  
Old 09-21-2012, 10:19 PM
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Re: Quadra Drive II vs. Quadra Trac II

Well I'm not so sure a locked center diff is so dangerous if the front and rear are open. I don't see Mitsu's flying off the roadway.

But if the WK2 can lock as needed, or nearly so (80%, no?), I'm all for letting her do her job. Last winter was so mild I never got to really test her out.

4hi locking would be good for when you are in snow as you can regularly go 50-100 miles at say 45 miles an hour without seeing a speck of dry pavement - at least where I live, and 4lo requires the lower speeds or stopping to revert to hi.

I guess the dccd dial on the STi would be ideal but I know that is a different vehicle.

What I get from this thread is the base Overland WK2 is about ready for the trail and I've been contemplating beefier tires and using it more off road versus keeping it strictly for pavement and hwy. So again, this thread helps sort things out a bit. Thanks.
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  #35  
Old 09-22-2012, 04:01 PM
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Old 09-22-2012, 11:33 PM
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Re: Quadra Drive II vs. Quadra Trac II

I think that's the first time I've seen pics of a WK2 SRT8 off road. How did it go?
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