Aero 4x4, how does it work
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From: Manton,MI
Aero 4x4, how does it work
I brought home an aero E4wd and I see that it has a 4x4 dash light. Does this light come on to tell you it has engaged 4x4 or is it for dignostic purposes? I'm assuming it has a sensor on both the rear and front outputs and automatically engages 4x4 when the sensors detect wheel slip? I guess what I'm looking for is a description on how the system works. Thanks RB
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From: SoCal
That light on the dash is for diagnostic purposes. When you first start the car, it comes on for a few seconds when the controller does some self tests. During normal operations, it stays off. It comes on during operation when the controller detects something wrong with the system.
Your guess about how it works is pretty much correct. Like Pablo says, the system is always 4wd, but the center differential is open to leave the system in 30/70 f/r drive. When the controller detects a certain amount of speed difference between the front and rear wheels, it will engage an electronic clutch in the center differential to lock it into 50/50 mode. It has some complicated decision algorithm for when and how to engage and dis-engage under what conditions. At worse, you get at least one front and one rear wheel driving, or one front and two rear wheels driving with limited slip rears. This give better driving traction than a 2wd with an open rear differential, which degrades to 1wd in very slippery conditions.
Your guess about how it works is pretty much correct. Like Pablo says, the system is always 4wd, but the center differential is open to leave the system in 30/70 f/r drive. When the controller detects a certain amount of speed difference between the front and rear wheels, it will engage an electronic clutch in the center differential to lock it into 50/50 mode. It has some complicated decision algorithm for when and how to engage and dis-engage under what conditions. At worse, you get at least one front and one rear wheel driving, or one front and two rear wheels driving with limited slip rears. This give better driving traction than a 2wd with an open rear differential, which degrades to 1wd in very slippery conditions.
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From: Manton,MI
Originally Posted by xlt4wd90
That light on the dash is for diagnostic purposes. When you first start the car, it comes on for a few seconds when the controller does some self tests. During normal operations, it stays off. It comes on during operation when the controller detects something wrong with the system.
Your guess about how it works is pretty much correct. Like Pablo says, the system is always 4wd, but the center differential is open to leave the system in 30/70 f/r drive. When the controller detects a certain amount of speed difference between the front and rear wheels, it will engage an electronic clutch in the center differential to lock it into 50/50 mode. It has some complicated decision algorithm for when and how to engage and dis-engage under what conditions. At worse, you get at least one front and one rear wheel driving, or one front and two rear wheels driving with limited slip rears. This give better driving traction than a 2wd with an open rear differential, which degrades to 1wd in very slippery conditions.
Your guess about how it works is pretty much correct. Like Pablo says, the system is always 4wd, but the center differential is open to leave the system in 30/70 f/r drive. When the controller detects a certain amount of speed difference between the front and rear wheels, it will engage an electronic clutch in the center differential to lock it into 50/50 mode. It has some complicated decision algorithm for when and how to engage and dis-engage under what conditions. At worse, you get at least one front and one rear wheel driving, or one front and two rear wheels driving with limited slip rears. This give better driving traction than a 2wd with an open rear differential, which degrades to 1wd in very slippery conditions.
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From: Kiev, Ukraine
RB! There is assimetrical diff inside t-case. Why assimetrical? To make awd van skid like RWD in sharp curve. Soviet Lada Nivas and Chevy Niva have 50/50 t-caSe diff and what axe amay skid first depends on current weight distribution and it is difficuylt to drive it in skid curve. Today ASR/ESP solves this proiblem
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Joined: Sep 2003
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From: SoCal
I'm not sure how an assymetrical diff works, without also changing the relative speed between the two sides; I just read that it's what the Aero has.
I'd like to take the manually activated clutch idea one step further, by also incorporating remotely lockable hubs in the front. That way, the entire front drivetrain would be inactive until you engage it. I wonder if the front locking hubs of an Explorer can be adapted?
I'd like to take the manually activated clutch idea one step further, by also incorporating remotely lockable hubs in the front. That way, the entire front drivetrain would be inactive until you engage it. I wonder if the front locking hubs of an Explorer can be adapted?
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From: Manton,MI
Originally Posted by ken1mod
I would like a switch on the panel to engage the center dif lock manually in bad conditions. I believe this is easy to do. Sometimes we are better than the silicon chips.
ken
ken
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From: Manton,MI
Originally Posted by xlt4wd90
I'm not sure how an assymetrical diff works, without also changing the relative speed between the two sides; I just read that it's what the Aero has.
I'd like to take the manually activated clutch idea one step further, by also incorporating remotely lockable hubs in the front. That way, the entire front drivetrain would be inactive until you engage it. I wonder if the front locking hubs of an Explorer can be adapted?
I'd like to take the manually activated clutch idea one step further, by also incorporating remotely lockable hubs in the front. That way, the entire front drivetrain would be inactive until you engage it. I wonder if the front locking hubs of an Explorer can be adapted?
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From: Rochester, NY
The center differential splits torque assymetrically between the front and rear axles, not speeds. The center differential is planetary, which means it has a sun gear, planetary gears around it, and an anulas around the planetaries with internal teeth (see pictures http://en.wikipedia.org/wiki/Epicyclic_gearing ).
Input torque is applied to the planetary gears by way of a carrier that they are mounted to on journal pins. The differential's outputs are the sun and the internal-tooth gear. Under straight line driving conditions, the entire assembly rotates as one unit at the same speed, just like an axle differential with bevel gears does. But since the one output is larger in diameter then the other, it receives a different amount of torque then the smaller one does because it basically has a longer lever arm then the other one. Remember that torque is force multiplied by distance - the greater the distance, the more torque you get for the same amount of force.
In the case of the Aerostar's planetary differential, the sun gear is coupled to the chain that drives the front driveshaft, and the internal gear drives through to the rear driveshaft. The size difference between the two gears determines what the split of the torque will be - in this case, 1/3 goes to the front and 2/3 goes to the rear. Marketing folks like nice round numbers, so they advertised it as 30/70 instead though. I guess that's easier to print in a brochure then 33.333333.../66.666666...
Input torque is applied to the planetary gears by way of a carrier that they are mounted to on journal pins. The differential's outputs are the sun and the internal-tooth gear. Under straight line driving conditions, the entire assembly rotates as one unit at the same speed, just like an axle differential with bevel gears does. But since the one output is larger in diameter then the other, it receives a different amount of torque then the smaller one does because it basically has a longer lever arm then the other one. Remember that torque is force multiplied by distance - the greater the distance, the more torque you get for the same amount of force.
In the case of the Aerostar's planetary differential, the sun gear is coupled to the chain that drives the front driveshaft, and the internal gear drives through to the rear driveshaft. The size difference between the two gears determines what the split of the torque will be - in this case, 1/3 goes to the front and 2/3 goes to the rear. Marketing folks like nice round numbers, so they advertised it as 30/70 instead though. I guess that's easier to print in a brochure then 33.333333.../66.666666...
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From: Rochester, NY
Originally Posted by xlt4wd90
I'd like to take the manually activated clutch idea one step further, by also incorporating remotely lockable hubs in the front. That way, the entire front drivetrain would be inactive until you engage it. I wonder if the front locking hubs of an Explorer can be adapted?
You could make the argument that by locking the center diff with the clutch (assuming you added a manual switch) so that the differential isn't an issue. The trouble with that is the clutch itself. It's not likely to have been sized for the duty cycle it would see being locked 100% of the time during 2WD operation, with 100% of the torque going across it. I think you'd have durability issues. If the center diff lock was actually a sliding collar/dog clutch, it would be a different story. But that isn't what we've got here.
At the same time, if all of that actually did work, you'd still be turning the front driveshaft regardless of whether or not you had disengagable hubs since you've locked up the center diff. The front driveshaft would be locked to the rear driveshaft, via the manual controlled clutch, and so it would be driven anyway. That means the front diff and axles are also going to be driven as well, so the axles will be turning at the same RPM as the wheels even though the hub is disengaged between them. So, you certainly have not saved anything in terms of drag, and in turn, fuel economy. Seeing as how there's no other real valid reason for disengaging the hubs in an AWD system, there would be no advantage to doing this...
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From: Manton,MI
Originally Posted by Torsen Rick
The center differential splits torque assymetrically between the front and rear axles, not speeds. The center differential is planetary, which means it has a sun gear, planetary gears around it, and an anulas around the planetaries with internal teeth (see pictures http://en.wikipedia.org/wiki/Epicyclic_gearing ).
Input torque is applied to the planetary gears by way of a carrier that they are mounted to on journal pins. The differential's outputs are the sun and the internal-tooth gear. Under straight line driving conditions, the entire assembly rotates as one unit at the same speed, just like an axle differential with bevel gears does. But since the one output is larger in diameter then the other, it receives a different amount of torque then the smaller one does because it basically has a longer lever arm then the other one. Remember that torque is force multiplied by distance - the greater the distance, the more torque you get for the same amount of force.
In the case of the Aerostar's planetary differential, the sun gear is coupled to the chain that drives the front driveshaft, and the internal gear drives through to the rear driveshaft. The size difference between the two gears determines what the split of the torque will be - in this case, 1/3 goes to the front and 2/3 goes to the rear. Marketing folks like nice round numbers, so they advertised it as 30/70 instead though. I guess that's easier to print in a brochure then 33.333333.../66.666666...
Input torque is applied to the planetary gears by way of a carrier that they are mounted to on journal pins. The differential's outputs are the sun and the internal-tooth gear. Under straight line driving conditions, the entire assembly rotates as one unit at the same speed, just like an axle differential with bevel gears does. But since the one output is larger in diameter then the other, it receives a different amount of torque then the smaller one does because it basically has a longer lever arm then the other one. Remember that torque is force multiplied by distance - the greater the distance, the more torque you get for the same amount of force.
In the case of the Aerostar's planetary differential, the sun gear is coupled to the chain that drives the front driveshaft, and the internal gear drives through to the rear driveshaft. The size difference between the two gears determines what the split of the torque will be - in this case, 1/3 goes to the front and 2/3 goes to the rear. Marketing folks like nice round numbers, so they advertised it as 30/70 instead though. I guess that's easier to print in a brochure then 33.333333.../66.666666...
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From: Manton,MI
Originally Posted by Torsen Rick
The inclusion of a center differential in the drivetrain prevents you from being able to disengage the front end, even if there were locking hubs and a manual control on the clutch.
You could make the argument that by locking the center diff with the clutch (assuming you added a manual switch) so that the differential isn't an issue. The trouble with that is the clutch itself. It's not likely to have been sized for the duty cycle it would see being locked 100% of the time during 2WD operation, with 100% of the torque going across it. I think you'd have durability issues. If the center diff lock was actually a sliding collar/dog clutch, it would be a different story. But that isn't what we've got here.
At the same time, if all of that actually did work, you'd still be turning the front driveshaft regardless of whether or not you had disengagable hubs since you've locked up the center diff. The front driveshaft would be locked to the rear driveshaft, via the manual controlled clutch, and so it would be driven anyway. That means the front diff and axles are also going to be driven as well, so the axles will be turning at the same RPM as the wheels even though the hub is disengaged between them. So, you certainly have not saved anything in terms of drag, and in turn, fuel economy. Seeing as how there's no other real valid reason for disengaging the hubs in an AWD system, there would be no advantage to doing this...
You could make the argument that by locking the center diff with the clutch (assuming you added a manual switch) so that the differential isn't an issue. The trouble with that is the clutch itself. It's not likely to have been sized for the duty cycle it would see being locked 100% of the time during 2WD operation, with 100% of the torque going across it. I think you'd have durability issues. If the center diff lock was actually a sliding collar/dog clutch, it would be a different story. But that isn't what we've got here.
At the same time, if all of that actually did work, you'd still be turning the front driveshaft regardless of whether or not you had disengagable hubs since you've locked up the center diff. The front driveshaft would be locked to the rear driveshaft, via the manual controlled clutch, and so it would be driven anyway. That means the front diff and axles are also going to be driven as well, so the axles will be turning at the same RPM as the wheels even though the hub is disengaged between them. So, you certainly have not saved anything in terms of drag, and in turn, fuel economy. Seeing as how there's no other real valid reason for disengaging the hubs in an AWD system, there would be no advantage to doing this...
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Senior User
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From: Manton,MI
Originally Posted by Torsen Rick
The center differential splits torque assymetrically between the front and rear axles, not speeds. The center differential is planetary, which means it has a sun gear, planetary gears around it, and an anulas around the planetaries with internal teeth (see pictures http://en.wikipedia.org/wiki/Epicyclic_gearing ).
Input torque is applied to the planetary gears by way of a carrier that they are mounted to on journal pins. The differential's outputs are the sun and the internal-tooth gear. Under straight line driving conditions, the entire assembly rotates as one unit at the same speed, just like an axle differential with bevel gears does. But since the one output is larger in diameter then the other, it receives a different amount of torque then the smaller one does because it basically has a longer lever arm then the other one. Remember that torque is force multiplied by distance - the greater the distance, the more torque you get for the same amount of force.
In the case of the Aerostar's planetary differential, the sun gear is coupled to the chain that drives the front driveshaft, and the internal gear drives through to the rear driveshaft. The size difference between the two gears determines what the split of the torque will be - in this case, 1/3 goes to the front and 2/3 goes to the rear. Marketing folks like nice round numbers, so they advertised it as 30/70 instead though. I guess that's easier to print in a brochure then 33.333333.../66.666666...
Input torque is applied to the planetary gears by way of a carrier that they are mounted to on journal pins. The differential's outputs are the sun and the internal-tooth gear. Under straight line driving conditions, the entire assembly rotates as one unit at the same speed, just like an axle differential with bevel gears does. But since the one output is larger in diameter then the other, it receives a different amount of torque then the smaller one does because it basically has a longer lever arm then the other one. Remember that torque is force multiplied by distance - the greater the distance, the more torque you get for the same amount of force.
In the case of the Aerostar's planetary differential, the sun gear is coupled to the chain that drives the front driveshaft, and the internal gear drives through to the rear driveshaft. The size difference between the two gears determines what the split of the torque will be - in this case, 1/3 goes to the front and 2/3 goes to the rear. Marketing folks like nice round numbers, so they advertised it as 30/70 instead though. I guess that's easier to print in a brochure then 33.333333.../66.666666...