2018 MR 130 Passenger XLT 3.7. Mods: Eaton Truetrac, Yukon 4.11, Cooper Discoverer AT3 245/70/16
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238 Posts
😳The system re-learns and heals itself every drive cycle

😳The system re-learns and heals itself every drive cycle
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.Mud rut turns off traction control, right?
Indeed. Mud-rut again. Good question.Greggoryx when you drove out did you select mud-ruts again? The AWD system will automatically revert back to normal drive mode when the ignition is turned off.
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"?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?
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?
All bone-stock including the tires. Just lowered the pressure so it was smoother while pushing the pace.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.
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"?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 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.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.
Yep, just a run-of-the-mill open diff. Nothing particularly interesting in there. AWD sends torque in, differential sends torque out.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.
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![]()
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.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.
This is exactly the type of terrain/surfaces the AWD system is designed for. You will be fine.I don’t plan on rough off roading. Got AWD for extra 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??
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 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
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.Thanks Van7 for the info. Now it comes back to me, it was the AWD temporarily disabled message i got on the display. Im sure due to it saving itself, but makes no sense as it failed that quickly. I would think i would get a little bit more before it shut down? Like the manual says, 2.5 miles in deep sand will make the system fail, but i didnt go anywhere near even a 1/4 mile before it shut off. I just dont trust it anymore and cannot rely on that system to save me unless there is a way to disable the safety feature of it saving itself and leaving me stranded. Sure wish someone had a dongle or something. (lol) I would by pass any factory safety setting in a heart beat as most often than not, it shuts down way before its close to failure. All i needed was 50 more feet and i would have been to the top.
This sounds like it was an F150 with a "4A" setting for its t-case?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.
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