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Electric vs manual 4x4


Flamemaster66
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Electronic anything is always something else that can break, but it sure seems like a relatively durable system based on the few problem posts on the board.

The only time I'd let it sway a purchase decision is if I really wanted to be able to put on manual hubs. Several people have had problems with it throwing errors running manual unlocked hubs. And of course the 4x4 switch wouldn't work without locking manual hubs first, and forgetting to lock before hitting the switch might damage the system.

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Most people would recommend the electronic setup for the AUTO mode that gives you all wheel drive with an open center diff. It’s fantastic for bad weather so that you can still turn without plowing through corners. But the flip side is the truck can get very confused if it’s in any other setup than stock because there’s so many sensors involved in running the TCase. 
 

Personally I don’t find that the electronic system is worth it. I’d swap in a manual in a heart beat if it were easy. I don’t trust a system I don’t fully understand and which has so many potential failure points. Same with the transmission, I’d prefer a manual

 

Edit to add:

 

My current plan is to add a rear air locker so that even if my 4WD system stops working on a trail, I’ll be able to use the locker to make the rear more effective and allow me to make it home

Edited by PathyGig12
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Electronic here: 227k miles and no issues. I’ve been running manual locking hubs since around 224k or 225k. No issues. Accidentally briefly engaged 4hi, and auto for a second at least once with hubs unlocked. No noises or lights on the dash happened. 

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Electronic here: 227k miles and no issues. I’ve been running manual locking hubs since around 224k or 225k. No issues. Accidentally briefly engaged 4hi, and auto for a second at least once with hubs unlocked. No noises or lights on the dash happened. 
Could you tell if the system engaged the front drive shaft? Or was it smart enough to know the speed difference between the front wheels and front drive shaft was too high and did nothing?

I think some of the people who reported problems were actually QX4s. I wonder if the system is any different.

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1 hour ago, colinnwn said:

Could you tell if the system engaged the front drive shaft? Or was it smart enough to know the speed difference between the front wheels and front drive shaft was too high and did nothing?

I think some of the people who reported problems were actually QX4s. I wonder if the system is any different.

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When i accidentally turned the dial  it was one of those "oh crap, what am I doing?" moments, so it was only engaged maybe 1-3 seconds. But no noises other than the actuator engaging like normal. Didn't feel any different either. But again, it was low speed, driving straight on rainy roads just a few feet for a few seconds doesn't give me much time to compare anything. Had I left it engaged, would something mess up or start making noises? Idk, but i have my doubts. 

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The problem with the electronic system is we don’t even understand how it works exactly. All evidence so far points to the fact that the front drive shaft continues to spin regardless of whether the hubs are locked or not, so I’m not entirely surprised that accidentally activating 4Hi didn’t harm anything. With the shaft still spinning it means the CVs must still be spinning inside the hubs, and that means giving them power would still not “break” anything. Eventually it would probably throw up a light because of the wheel speed sensors though 

 

The reason the front shaft still spins is not entirely understood, but I’ve been told it’s because of the clutch plates being partially engaged. So either it’s an issue with the TCase being confused, or maybe just normal operation that the clutch plates never disengage fully. Either way, it makes manual hubs much trickier because there’s no telling what’s really being done to the internals. I’ve had my Warn hubs for the last 15K miles and no real issues except a weird vibration that may or may not be related but sometimes goes away at high speeds and stays gone for the rest of a drive, which seems suspiciously like a TCase thing

 

 

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Spin an egg on the table, now stop it very briefly and let go... it will try to start spinning again because you stopped the shell but not the fluid inside. Moving parts next to other moving parts will translate some fluid friction. If its a clutch type engagement the moving parts are really close to each other so lots of fluid friction is translated over.
This is actually how torque converters and viscous differentials work but the fluid energy transfer is maximized even more by way of specially shaped turbines.

I've run out of time to go in depth, but in a nutshell I prefer manually shifted 4x4 for off roading vehicles and true AWD systems for street vehicles that may encounter adverse conditions. (r50/qx4 auto mode is not true AWD...)

Edited by MY1PATH
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5 hours ago, colinnwn said:

Could you tell if the system engaged the front drive shaft? Or was it smart enough to know the speed difference between the front wheels and front drive shaft was too high and did nothing?

I think some of the people who reported problems were actually QX4s. I wonder if the system is any different.

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The ATTESA 4wd system uses a small torque converter with a lockup clutch to split power to the front wheels. Therefore, the maximum torque split to the front is 50%. The rear end is always directly and mechanically driven, so even if you accidentally stick it in AUTO with the front hubs unlocked you won't notice any loss of drive. It may damaged the transfer if you left it in for too long though.

 

When in low range, there is a locking spline inserted that mechanically locks the transfer into a 50:50 torque split. So if you're in low box already, even if all the electrics crap out you're still mechanically centre locked and in low box. Trouble might be disengaging it...

 

Personally I've never had any troubles with the 4-mode system in either my r50 or r51 Pathies. My R50 was the older design with the dial for 2wd auto and lock, and the lever for low box though.

 

The QX4 is mechanically identical.

Edited by KiwiTerrano
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1 hour ago, MY1PATH said:

Spin an egg on the table, now stop it very briefly and let go... it will try to start spinning again because you stopped the shell but not the fluid inside. Moving parts next to other moving parts will translate some fluid friction. If its a clutch type engagement the moving parts are really close to each other so lots of fluid friction is translated over.
This is actually how torque converters and viscous differentials work but the fluid energy transfer is maximized even more by way of specially shaped turbines.

I've run out of time to go in depth, but in a nutshell I prefer manually shifted 4x4 for off roading vehicles and true AWD systems for street vehicles that may encounter adverse conditions. (r50/qx4 auto mode is not true AWD...)

When you have a minute, I’d love to hear more about this.
 

Are you suggesting that motion in the Tcase is translating to the front shaft through a fluid friction interaction which keeps the front spinning even when the clutch plates are disengaged?
 

Id just really love to see the inner workings of the Tcase and what happens under different conditions to demystify this whole thing

 

I can say that the last couple times I’ve been off-road I’ve had the hubs locked and the truck in 4Hi and noticed every once in a while I’d get a steady 4WD light on the dash If I was doing a tight turn or reversing awkwardly. It also happened once in 4low. As soon as I restarted the truck, the light was gone. Whether this is a damage related issue or maybe an oil temp issue, I have no idea. But I’ll say this......it never happened before I put the manual hubs on so I can’t rule out the possibility that some kind of damage is being done to the clutch plates 

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When you have a minute, I’d love to hear more about this.
 
Are you suggesting that motion in the Tcase is translating to the front shaft through a fluid friction interaction which keeps the front spinning even when the clutch plates are disengaged?
 
Id just really love to see the inner workings of the Tcase and what happens under different conditions to demystify this whole thing
 
I can say that the last couple times I’ve been off-road I’ve had the hubs locked and the truck in 4Hi and noticed every once in a while I’d get a steady 4WD light on the dash If I was doing a tight turn or reversing awkwardly. It also happened once in 4low. As soon as I restarted the truck, the light was gone. Whether this is a damage related issue or maybe an oil temp issue, I have no idea. But I’ll say this......it never happened before I put the manual hubs on so I can’t rule out the possibility that some kind of damage is being done to the clutch plates 
Do you need a copy of the service manual? It should show a basic description and some troubleshooting.

It's interesting the light has only come on with the hubs locked and in 4hi. With the hubs locked its mechanically identical to the factory drive flanges. I actually thought that light comes on and stays on while in 4wd. That's how my mechanical system worked.

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I can see how the ATX14A's auto mode would be nice in some settings, like a wet road with ice patches, or handing the keys to someone who isn't experienced at driving in snow. The TX10A can be a little clunky sometimes. That said, the ATX14A uses two hydraulic pumps, a wet clutch pack, an actuator, and a computer to do what the TX10A does with mechanical shifter and a little thought on your behalf. Kinda like the automatic hubs on the WD21. It's a neat idea, and I get why some people like it, but IMO it's more trouble than it's worth.


And yes, the ATX14A is not a true center diff. It contains a clutch pack, like what's in an automatic transmission, which the computer engages to send power to the front wheels when it thinks the rears are slipping. I think some AWD crossovers use a similar system, though typically the other way around (front wheel drive until the rear is needed). Clutch packs have a little drag when they're not engaged, I assume mostly due to the fluid being dragged around between them like My1Path said. An automatic transmission in neutral will still spin its output if there's nothing holding it (which is why you have to shift quickly between high and low range with a TX10A, or your auto trans will spin up its output while the transfer's in neutral and prevent you from completing the shift). It makes sense then that the clutched front output of the ATX14A would tend to spin when the rest of the drivetrain spins, even with the hubs and clutch disengaged. I doubt this is hurting anything, unless the clutch is less like an auto trans clutch than I think it is, or unless the computer does something dumb in response to what it thinks is a problem.

 

I don't have confirmation on this, but my theory as to why some trucks code with the auto transfer and manual hubs and some don't is that some trucks get their front wheel speed info from the ABS sensors, and others get it from a sensor on the front transfer case output, depending on whether they've got VDC. If the transfer output is spinning slower than the wheels, or not at all, and that's what the computer is watching to see what the front wheels are doing, it stands to reason it would get a little confused.

 

The only resource I've found for understanding what goes on in the ATX14A is the TF section of the service manual. The pictures don't move, but they're the best view you'll get short of disassembling one.

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I have a 04 Platinum with the electric t case. I am on 33s with 2 in lift springs and the lr 9449s. I obviously would prefer a manual transfer case because of the "cool" aspect but other than that i have had no problems what so ever. When i put on the manual hubs it took away the convenience of having the AUTO mode. The idea of having to get out of the car and lock the hubs during a bad storm so i can drive with AWD is unnecessary to me due to just laziness. So i wouldnt say that AUTO mode is a luxury unless you keep the factory hubs. I do want to make a note that after i did put on the manual hubs, i get a 4WD warning light when i take exteneded hour or longer trips on the highway at 65mph+. I dont worry about this because i assume it is just the computer getting confused. 

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8 hours ago, KiwiTerrano said:

The ATTESA 4wd system uses a small torque converter with a lockup clutch to split power to the front wheels.

This is wrong, I have r33 GTR transfer case (ATTESA) in the garage.
It uses a clutch pack in a basket/drum similar to a motorcycle clutch. A transfer case chain similar to the Pathfinders TX10 chain is attached to a basket/drum around the rear output shaft. The alternating clutch plates transfer torque from the rear output to the chain which then turns the front driveshaft. Instead of a clutch spring, an electric pump pressurizes a hydraulic system to apply pressure against the the clutch pack, its literally just a hydraulic piston. A PWM solenoid valve on the return line regulates the system pressure from 20~200 psi and this is controlled by the ATTESA computer.

While ATTESA is an AWD system, it is a transferase system (not a center differential). The rear wheels are always powered regardless of how much torque is sent to the front wheels.
Simplified:
In a transfer case system, if you stop the permanently driven wheels then everything stops.
But in a center diff system, if you stop ANY pair of wheels the other pair will continue to spin.

 

 

Edited by MY1PATH
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I wonder how quickly the auto system works and if it has any stability improvement.

In Dallas there is a loop over to an overpass, and right at the merge there is a bouncy lip transition to slick asphalt.

Twice when it's been rainy, even though I was using barely any throttle to just maintain speed, when the rear wheels went over that lip the truck violently swung its butt around to where I was almost 80 degrees to the direction of travel. I lifted off the throttle and gently countersteered, and it swiped back the other way almost as violently. It took 2 swings back and forth to get it under control. I've wondered if the limited slip diff in 2 wheel mode made that worse.

I got to where going over the lip I took my foot off the throttle completely and let it coast for a bit onto the asphalt.

I know the R50 auto mode isn't meant for vehicle stability assist, but I wonder if it can react fast enough to sudden large wheel speed changes to dampen oscillations like that.

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On 10/16/2020 at 5:14 AM, MY1PATH said:

This is wrong, I have r33 GTR transfer case (ATTESA) in the garage.
It uses a clutch pack in a basket/drum similar to a motorcycle clutch. A transfer case chain similar to the Pathfinders TX10 chain is attached to a basket/drum around the rear output shaft. The alternating clutch plates transfer torque from the rear output to the chain which then turns the front driveshaft. Instead of a clutch spring, an electric pump pressurizes a hydraulic system to apply pressure against the the clutch pack, its literally just a hydraulic piston. A PWM solenoid valve on the return line regulates the system pressure from 20~200 psi and this is controlled by the ATTESA computer.

While ATTESA is an AWD system, it is a transferase system (not a center differential). The rear wheels are always powered regardless of how much torque is sent to the front wheels.
Simplified:
In a transfer case system, if you stop the permanently driven wheels then everything stops.
But in a center diff system, if you stop ANY pair of wheels the other pair will continue to spin.

 

 

 

That's exactly what I said...

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