Both drive shafts turn at all time. The rear driveshaft is always connected to the rear wheels and differential which all move whenever the vehicle is in motion.
4WD vs Auto Shaft Effect
Out of curiosity, I observed the action of the drive shaft in forward and reverse in my short driveway with the 4WD button off and on. The shaft spun in all four conditions.
I was under the impression that the shaft is disengaged and stationary with the 4WD button off and the system in "auto" until traction conditions call for it.
Misunderstanding? Malfunction? Anyone?
Thanks in advance.
I was under the impression that the shaft is disengaged and stationary with the 4WD button off and the system in "auto" until traction conditions call for it.
Misunderstanding? Malfunction? Anyone?
Thanks in advance.
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Thanks for the clarification. I found the video that caused my confusion. Give this a watch and see if you think it's incorrect or just misleading in presentation.Both drive shafts turn at all time. The rear driveshaft is always connected to the rear wheels and differential which all move whenever the vehicle is in motion.
GKN has a good illustration on our 4x4 system. But all bets are off if doing any testing/observation in "Auto" mode. Some sources states the system goes to FWD mode only in steady-state cruise conditions. Also "Auto" does some preemptive thinking and keeps the drive shaft connected on take-offs (manual states heavy acceleration or something like that?) in addition to outside temperature, rain-detection and whatever else packed in their algorithm.
Well, looks like my data is certainly skewed then. While I wasn't performing any acceleration during the experiment, it was pretty cold and wet LOLGKN has a good illustration on our 4x4 system. But all bets are off if doing any testing/observation in "Auto" mode. Some sources states the system goes to FWD mode only in steady-state cruise conditions. Also "Auto" does some preemptive thinking and keeps the drive shaft connected on take-offs (manual states heavy acceleration or something like that?) in addition to outside temperature, rain-detection and whatever else packed in their algorithm.
Yeah, I did some investigation into how our 4WD system works. My head started hurting, and I still didn't fully understand it. Pretty complex stuff.
Here's another web site that explains how the system works -- or tries to. Someone referred me to it (hopefully you know who you are, because I can't remember...
):
Fiat 500 USA: Fiat 500X All Wheel Drive System Explored
But yeah, the drive shaft apparently turns all the time. Normally on the road, only the front wheels are driven, right? (Even on the 4Xe?) But the drive shaft still turns.
The entire 4WD engagement is done at the rear differential.
I suppose that's because when you shift into 4WD (or the Renegade does automatically), it doesn't have to overcome the inertia of the shaft in order to get things turning in back...
Here's another web site that explains how the system works -- or tries to. Someone referred me to it (hopefully you know who you are, because I can't remember...
):Fiat 500 USA: Fiat 500X All Wheel Drive System Explored
But yeah, the drive shaft apparently turns all the time. Normally on the road, only the front wheels are driven, right? (Even on the 4Xe?) But the drive shaft still turns.
The entire 4WD engagement is done at the rear differential.
I suppose that's because when you shift into 4WD (or the Renegade does automatically), it doesn't have to overcome the inertia of the shaft in order to get things turning in back...
The rear driveshaft is always connected to the rear axle. If the rear wheels are spinning, the driveshaft is turning. That does not necessarily mean the driveshaft is being driven by the transmission or transfer case. That will depend on what selection you pick in your transfer case.
My understanding is:
FWD unless slip is detected and power is sent to the back.
The rear driveshaft is not connected until power is shifted, or you push 4WD lock. In which case it is permanently connected.
(4Xe is a totally different beast. You can run in petrol FWD, electric RWD or hybrid AWD.)
FWD unless slip is detected and power is sent to the back.
The rear driveshaft is not connected until power is shifted, or you push 4WD lock. In which case it is permanently connected.
(4Xe is a totally different beast. You can run in petrol FWD, electric RWD or hybrid AWD.)
The (only) driveshaft is not connected to the rear differential until power is shifted, or you push 4WD lock.The rear driveshaft is not connected until power is shifted, or you push 4WD lock.
The driveshaft is always connected to the rear axle. It is not driven, or powered, until you place it in 4wd or it senses wheel spin. If anyone doubts this, please jack up the rear wheels and turn them.The (only) driveshaft is not connected to the rear differential until power is shifted, or you push 4WD lock.
Hmmm... Depends what you mean by "connected." Remember that AtomicHog's original post was about the fact that the was seeing the drive shaft (propeller shaft) turning whether the vehicle was in 2WD or 4WD.The driveshaft is always connected to the rear axle. It is not driven, or powered, until you place it in 4wd or it senses wheel spin. If anyone doubts this, please jack up the rear wheels and turn them.
I'm looking at Fiat 500 USA: Fiat 500X All Wheel Drive System Explored again. About a quarter of the way down, under "Propeller Shaft," it says that "the PTU [at the engine] always keeps the propeller shaft engaged when starting from a standstill or speeds close to 0 km/h (0 mph)." Which is why AtomicHog always saw his driveshaft/propeller shaft turning in his driveway.
And that "[t]he propeller shaft disengages when the car exceeds a set speed; the engine load is not too high and the road conditions are ideal."
And then re-engages under certain conditions.
At the same time, the Rear Drive Module separately engages and disengages the rear wheels -- to allow them to free-wheel in 2WD, and be driven in 4WD.
Complex as hell. And fine, as long as everything works.
So I was incorrect -- the driveshaft/propeller shaft doesn't turn all the time. But it's also not dependent on 2WD or 4WD.
Thanks for taking the time to parse this out. Sounds like if someone had a camera attached underneath and pointed at the propeller shaft (while driving), they'd see the shaft intermittently rotate and stop depending on vehicle speed and engine load. Regardless of the position of the 4x4 switch/knob. Got it.Hmmm... Depends what you mean by "connected." Remember that AtomicHog's original post was about the fact that the was seeing the drive shaft (propeller shaft) turning whether the vehicle was in 2WD or 4WD.
I'm looking at Fiat 500 USA: Fiat 500X All Wheel Drive System Explored again. About a quarter of the way down, under "Propeller Shaft," it says that "the PTU [at the engine] always keeps the propeller shaft engaged when starting from a standstill or speeds close to 0 km/h (0 mph)." Which is why AtomicHog always saw his driveshaft/propeller shaft turning in his driveway.
And that "[t]he propeller shaft disengages when the car exceeds a set speed; the engine load is not too high and the road conditions are ideal."
And then re-engages under certain conditions.
At the same time, the Rear Drive Module separately engages and disengages the rear wheels -- to allow them to free-wheel in 2WD, and be driven in 4WD.
Complex as hell. And fine, as long as everything works.
So I was incorrect -- the driveshaft/propeller shaft doesn't turn all the time. But it's also not dependent on 2WD or 4WD.
Which raises the question, what does the switch/knob do? Seems it'd at least prevent the prop shaft from dropping out of rotation with "4WD LOCK" selected.
Good question. Owner's Manual is really vague about this sort of stuff... "Don't you worry your little head about the details." Sure would be nice to know exactly what happens.Which raises the question, what does the switch/knob do? Seems it'd at least prevent the prop shaft from dropping out of rotation with "4WD LOCK" selected.
I'd imagine that "4WD LOCK" means exactly that... and that other wise, it's not locked...
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