2018 MR 130 Passenger XLT 3.7. Mods: Eaton Truetrac, Yukon 4.11, Cooper Discoverer AT3 245/70/16
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AWD system shut down
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Reviving this thread since I (personally) just experienced the "AWD Temporarily Disabled" feature. My (adult) son had experienced it previously, but... never sure about things until I experience them personally.
Conditions: left Benton Crossing Road onto about six miles of fire-roads to the Catacombs area near Casa Diablo Mountain. This is a rutted, rocky fire-road with intermittent washboards (though not non-stop washboard like Buttermilk Road) but very little up/down - pretty level. Lots of tight-ish squeezes between rocks and/or trees and frequently deciding between staying in the ruts or running along the high-center and high-side. Low technical for "off-road" but pretty high technical for "fire-road."
Switched to Mud-Rut almost immediately - son remembered that it mattered from his experience. Ran great on the way out - being fairly cautious and listening for how many bolts would fall out along the rutted-up road in our various aluminum modules (roof-rack / solar, bed, fridge cabinet, galley). Average speed probably in the 10-15mph range.
Buddy that met us there has an almost-identical 2020 HR-Ext EB - but 2WD, not AWD or LSD (we have both). We wondered how different they might feel and I was saying it's too bad I can't just turn mine off to see.
On the way back, not so cautious. We'd tightened up a couple bolts that seemed loose and I was giving it a bit more "go." And curious just how much time that 6-ish miles would take if I let it rattle a bit more. Near five miles later, get the "AWD Temporarily Disabled" message. Figured that's cool... get to see how 2WD feels. It was a little less connected to the fire-road - bit more wander and the front end had that too-much-power-steering feel to it. Didn't slow down, though. Minute or two later, it did "AWD Restored" and everything was back to normal. Average speed more 15-20mph.
Didn't turn off/on (as son did previously) and didn't ease off (too curious).
Sure would be cool if it didn't do that. But not terrible in this case. Thought I'd share for anyone else who experiences it.
Conditions: left Benton Crossing Road onto about six miles of fire-roads to the Catacombs area near Casa Diablo Mountain. This is a rutted, rocky fire-road with intermittent washboards (though not non-stop washboard like Buttermilk Road) but very little up/down - pretty level. Lots of tight-ish squeezes between rocks and/or trees and frequently deciding between staying in the ruts or running along the high-center and high-side. Low technical for "off-road" but pretty high technical for "fire-road."
Switched to Mud-Rut almost immediately - son remembered that it mattered from his experience. Ran great on the way out - being fairly cautious and listening for how many bolts would fall out along the rutted-up road in our various aluminum modules (roof-rack / solar, bed, fridge cabinet, galley). Average speed probably in the 10-15mph range.
Buddy that met us there has an almost-identical 2020 HR-Ext EB - but 2WD, not AWD or LSD (we have both). We wondered how different they might feel and I was saying it's too bad I can't just turn mine off to see.
On the way back, not so cautious. We'd tightened up a couple bolts that seemed loose and I was giving it a bit more "go." And curious just how much time that 6-ish miles would take if I let it rattle a bit more. Near five miles later, get the "AWD Temporarily Disabled" message. Figured that's cool... get to see how 2WD feels. It was a little less connected to the fire-road - bit more wander and the front end had that too-much-power-steering feel to it. Didn't slow down, though. Minute or two later, it did "AWD Restored" and everything was back to normal. Average speed more 15-20mph.
Didn't turn off/on (as son did previously) and didn't ease off (too curious).
Sure would be cool if it didn't do that. But not terrible in this case. Thought I'd share for anyone else who experiences it.
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Mud rut turns off traction control, right?
That was reported earlier in the thread... but not sure that's what we saw. I'll make another attempt to break it again eventually.
Indeed. Mud-rut again. Good question.
We've since experienced this numerous times. It happens the least with mud-rut but is pretty much a given that it will occur if we're moving fast on low-traction roads.
One adventure - documented here, I think - we lowered the tire pressure down for a 10+ mile drive on White Mountain road - mostly clean gravelly fire-road - and it still did it. Of course, we were doing 40mph, so... bound to find the limit, I guess?
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That seems really odd for the system to be shutting down on just a dirt road. I can see traction control turning off to save the brakes from excessive heat but the AWD system? Are you pushing it really hard like pre-running in order to get it to turn off? Does it always come back on after a few minutes?
I agree, it should be able to run all day on those kinds of surfaces. Do you have four same/similar tires on the van? Is the message "AWD Off" or "AWD temporarily disabled"?
The temporarily disabled is generally due to heat being detected in various parts of the system, although there are no actual sensors, it's all analytical heat assessment. If there is a ton of noise on the wheel speed inputs due to traveling rapidly on rough/irregular surfaces, it's possible to gradually ratchet up the calculated temperatures, but this is pretty unlikely and difficult to actually achieve.
All bone-stock including the tires. Just lowered the pressure so it was smoother while pushing the pace.
Can't be sure what message it was. That was a while ago. Pretty sure it was the "temporarily" thing on the really rough road; but it might have been more than that on the faster, smoother road. At this point, I've come to expect / accept that it's going to do it whenever I'm pushing it on rough dirt roads. I'm sure it'll come back up in a couple months when I'm out on dirt roads again (more snow right now) and I'll see what it says.
2021 3.5 Litre AWD Cargo To Campervan Conversion In Progress
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OK< so there is a servo operated clutch in the transfer case. But what is in the PTU? Is it a wee little differential? Sprag clutch? Black magic? Magic beans?I have a transfer case from an AWD Transit opened up on my bench right now. Got tired of so little information available from Ford so I bought one and disassembled it. I can say with a high amount of confidence that the issue you had with the AWD system is 100% due to the AWD control module software and how it handles (...or in your case chokes on and errors out because of...) the incoming wheel speed data. The transfer case mechanicals internally are simple. The encoder motor that controls the front drive engagement is simple and provides the module with nothing other than a positional signal (there is no temperature sensing of the t-case or the encoder motor in the system). The "AWD" engagement is all handled by the module and the algorithms (which are different depending on the drive mode selected) and the math behind relative wheel speeds vs. throttle position vs. output shaft speed and any number of variables Ford has chosen to use. It's possible that the module itself has a temp sensing shutdown mechanism, after all it is engaging/disengaging a 20amp motor in real-time based on how the wheel speeds are interpreted. I could see the module heating up quickly if it was having to "work" a lot to manage the response to the drive mode algorithm but I don't see the motor having any issues because it doesn't actually see any significant load.
Which component are you referring to as the "PTU"?
Power flows from the engine straight back through the trans and t-case. The t-case sends torque primarily to the rear axle while syphoning some amount off to the front axle, depending on the level of engagement of the motor-actuated clutch pack. You're correct that it uses a chain to transfer torque between its two shafts. Finally, the hypoid gears in the differentials turn the torque 90 degrees out to the wheels.
There is no Power Takeoff Unit in this system or any conventional RWD/longitudinal 4x4 system with a t-case. FWD AWD typically uses a PTU to turn torque 90 degrees from the transverse mounted engine/transaxle back to the rear wheels.
No magic beans in the hardware, they're all in the software/controls system.
2021 3.5 Litre AWD Cargo To Campervan Conversion In Progress
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I am told the small box of gears in the front axle is a PTU. Is it a differential then? It is very small and holds a tiny amount of oil.
Yep, just a run-of-the-mill open diff. Nothing particularly interesting in there. AWD sends torque in, differential sends torque out.
FWIW, the only way to bias torque across the front axle or prevent slip up front is by traction control. So if front end grip is lacking, blame the tires or the brakes, not the AWD
2021 3.5 Litre AWD Cargo To Campervan Conversion In Progress
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No issues with my AWD, but I can't see the open diff in those PTU units. There are a few videos of them being opened, I don't see an open diff.Yep, just a run-of-the-mill open diff. Nothing particularly interesting in there. AWD sends torque in, differential sends torque out.
FWIW, the only way to bias torque across the front axle or prevent slip up front is by traction control. So if front end grip is lacking, blame the tires or the brakes, not the AWD
I don’t plan on rough off roading. Got AWD for exstra traction like mountain
travel in winter for some snow activities, slippery dry summer Forrest roads
to trailheads. So If I go up a long dry Forrest road with some good grades
but taking it easy 10/20 miles hour one may still encounter AWD shut down??
and its like more than 15 miles of it
travel in winter for some snow activities, slippery dry summer Forrest roads
to trailheads. So If I go up a long dry Forrest road with some good grades
but taking it easy 10/20 miles hour one may still encounter AWD shut down??
and its like more than 15 miles of it
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I’ve taken my van on long dirt roads and off-road trails and no shut downs yet for me. (Mud/ruts mode). I’ve only heard of a couple vans having this problem
Ah, make sure these aren't European Transits in the videos. They've had AWD for years, but the Euro AWD hardware is very different from what goes into the North American AWD Transits. Theirs is a hydraulic system and it's housed in the front axle so if you're seeing some interesting components in there, it may be a European vehicle/video and it probably doesn't match what's in your van.
This is exactly the type of terrain/surfaces the AWD system is designed for. You will be fine.
Also, see below...
I agree with @ArgonautVans, I think the vans experiencing these issues off road (even in relatively tame terrain) may have some other issue going on. There are things that can actually shut down AWD, like using a smaller spare tire, having mismatched axle ratios, or especially, having a faulted ABS wheel speed sensor.
I've driven a lot of miles in AWD Transits in all kinds of terrains, from stuff they're intended to drive in to stuff they are most definitely not, and the AWD Off message is very unusual (a small spare tire will trigger it, but that's by design). The system as a whole is pretty capable - your ground clearance, departure angle, and tires will become a limiting factor before the t-case gives you any issues off road.
Hopefully this helps with your decision / questions. Feel free to reach out to me via DM with any specific questions.
The Transit AWD (for North America) uses the same Transfer Case as the current generation Explorer.
The prior two generation Explorers did have a PTU, because they were transverse powertrains. You tube algorithms are probably showing Explorer videos because of the shared powertrain components, but those algorithms are really only designed to make you click and watch. They really don't care about promoting accurate content. It's all about the clicks.
The prior two generation Explorers did have a PTU, because they were transverse powertrains. You tube algorithms are probably showing Explorer videos because of the shared powertrain components, but those algorithms are really only designed to make you click and watch. They really don't care about promoting accurate content. It's all about the clicks.
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Fwiw, as an F150 driver, I was stuck once in a rut but could not get out. The 4x4 low would disengage whenever wheel spin hit a threshold. And the power was never adequately transferred to the opposite wheels. I was a noob with the system an learned the hard way.
Worse yet, while thankful for the help, was that I was pulled out of the rut by a neighbor with a jeep. He was running 37" wheels a Ford 460 engine with a Detroit locker rear end. Pretty bad ass. He was less than 1/2 my weight and yanked me out with ease. My street tires didn't help either.
I cursed the system and was shocked that the 4x4 is never a true 4x4 after wheel spin override. Live and learn.
This sounds like it was an F150 with a "4A" setting for its t-case?
If so, then yes it is possible to overpower the clutches in certain situations. Using 4L does not help. If the t-case is healthy it will not happen very often. Technically it's not a wheel spin threshold, if you're spinning the rear wheels and not the front, that slip is all going across the clutch. Like any clutch it doesn't like heat so it's designed to open up to keep from ruining itself and having to replace the whole t-case.
This is an unfortunate trade off of the nice smooth fulltime AWD systems. A locking 4x4 t-case would not be susceptible to that, but it also has terrible road manners and is clunky driving on road in rain or light snow, stuff like that, which is where AWD excels.
I will say, if you are traction limited (like spinning tires in a muddy rut) then adding torque by using 4L is not the answer. 4L is not an "extra-capable" 4x4 mode to use when AWD or 4H are not working. It has its places, but primarily it's for very low speed, technical creeping or very fine throttle control, like places where you need to keep your engine speed up in the powerband but the resulting vehicle speed would be too high in normal/high range. The engine always makes the same amount of torque, which is going to be sufficient to power the vehicle and probably slip the tires almost anywhere. 4L just takes that engine torque and multiplies it by the ratio in the t-case, meaning you have even more torque available to slip the tires and get stuck.
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