Good explanation - thanks. Things can get lost in translation sometimes
The CX-5 AWD suspends power to the rear wheels when the speed differential between the front and rear is too great. This info comes from Mazda N. America Service Info (see last sentence of the image below).
True. But based on my many years experience off-road with many different systems, there are serious misconceptions about how the various systems perform in various situations. I get tired of repeating myself but old misconceptions die hard.
ECU controlled AWD is far superior to 4WD for driving on slippery ice. On slippery ice the computer controls react in milliseconds and can independently apply individual brakes to instantly increase torque to the wheel(s) that are not slipping. The fact that this does not happen in the Subaru demonstration video until the very end is due entirely to the fact that the driver keeps the speed differential between f/r too high until the finish (which causes the Control Module to suspend power transfer to the rear wheels until the operator reduces the speed of the spinning tires). This protects the electronically controlled AWD clutch pack from over-heating. As soon as the speed of the spinning tires are reduced, the clutch transfers power to the rear wheels. Limited slip differentials are crude compared to an open differential with computer controlled independent braking. LSD's have serious limitations when friction levels approach or exceed the friction levels in the mechanism itself. They simply fail to transfer power as intended when both tires have very low traction (like on melting ice). However, an open differential with computer controlled independent braking can simulate a limited slip differential without the disadvantages inherent with LSD's. Specifically, on slippery ice a LSD if a crude device and friction inherent within the system can cause both tires on the axle to break traction. Computer controlled open differentials are much more sensitive.
Moving on to 4x4 with locking differentials, they are awesome for steep, rugged trails, rock crawling, etc. but are virtually useless for driving on slippery roads where an AWD like the CX-5 will literally drive circles around a vehicle with a locked differential. But AWD neophytes think it is the holy grail of snow/ice performance. They have obviously never driven a vehicle with a locking differentials on an icy road. And 4x4 with locking differential is COMPLETELY USELESS for the common winter conditions of patchy ice on mostly bare pavement. Anyone who has tried to drive a full locker on bare pavement will understand why the lockers must be kept un-locked and the hubs disengaged in this common winter condition. This leaves you with RWD and open differentials!
And yet the fact remains, the CX-5 is capable enough off-road to do any reasonable challenge thrown at it (assuming it is properly operated). This means you don't drive it onto ball bearing rollers and keep the gas pedal mashed. When you feel slip, modulate the throttle to reduce wheel spin. This causes power to transfer to the rear which will drive you forward. It works in reverse too. Any vehicle can get stuck but you would have to be a complete moron to get stuck in an AWD CX-5.
Speaking of morons, this guy in a Jeep Cherokee trying to get out of his parking space has got to take the cake (NSFW warning-strong language!):
https://www.youtube.com/watch?v=CuTXUcoGdhwv
Good point. Not to mention that fully-locking differentials are of very limited use.
Unobtanium drove his expensive, gas-guzzling, unreliable Cherokee two or three times in a snow event and now he thinks he's a winter driver, pretty hard to achieve when you live in Arkansas and don't participate in winter sports.
Yes, always put more faith in real world scenario's like the hill climb video I posted of my CX-5 rather than rigged tests using drivers who are trying to fail.
This is the system on the RAV4 Compare them with the pdf’s earlier in this thread and you will see they are the same.
The only exception is that the RAV has a lock switch and all that does is lock up the drive unit until 25mph where it drops out to save wear on the transmission and tires.
Your CX5 does not have a diff locker, it locks the wheels by applying brake pressure to each side wheel as required. It has exactly the same effect in that the torque is applied to the wheel with the best grip on the road. The Jeep as I’ve discovered since talking to you has a multi plate diff lock which can lock up all the axle but it can’t completely transfer all the drive to one wheel. This is a picture I found;
.....and this is the explanation;
Quadra-Drive II
The Quadra-Drive II Jeep 4 x 4 system offers owners the ultimate in off-road capability. It combines the NV245 full-time transfer case with Electronic Limited Slip Differentials (ELSD) for best-in-class tractive performance. The system instantly detects tire slip and smoothly distributes engine torque to the tires with traction. In some cases, the vehicle will even anticipate low traction and adjust to proactively limit or eliminate slip
The heart of the system is the NV245 active transfer case. This transfer case includes a center differential coupled with an electronically controlled clutch pack, varying it from a completely open state to completely locked, and infinite possibilities in between. The 4-Low gear ratio is 2.72:1.
Quadra-Drive II features an electronic shift mechanism with a unique engagement lever. The lever is conveniently located on the shift console. Pulling the lever up engages 4-Low. The lever returns to a resting position after activation. The transfer case also includes a neutral position for trouble-free towing vehicles, such as behind a motor home.
A key component in the Quadra-Drive II system is the ELSD – an industry first application – and the new benchmark for automatic traction differentials. The ELSD use electronically controlled clutch packs to automatically and instantly vary from slip to lock at each axle. This maximizes traction when needed without any of the on-road drawbacks normally associated with such a robust 4 x 4 system.
All components of the system work together, continually monitoring needs, to provide smooth and automatic application of the components for best-in-class tractive performance while improving the day-to-day on-road driving experience. For example, the ELSD releases the clutch packs in the front axle during turns to allow differentiation and prevent crow hop.
So now if we compare;
Both the CX5 and the jeep have an “always engaged” transfer box.
The Jeep uses a cross axle multi plate clutch to lock up both sides of the axle/The CX5 uses the brakes to lock the spinning wheel and transfer drive to the gripping wheel.
The Jeep COULD unlock the diff and transfer drive to one wheel but ONLY by using the ABS pump to apply the brake on the opposite side/The CX5 can do exactly the same thing as the diff is never locked
Right! Now onto this snow tire thing. In the video, Mr Angry gets out of his car at one point and in his temper he leaves the car in drive with the handbrake off. While he is out of the car you can see the wheels at the front and back turning. The fact that he is stuck is nothing to do with his obvious incompetence, it is because the tires are not getting grip in the snow. The difference between normal all season tires and winter tires in the snow is not insignificant, it is night and day. They are unbelievably different and the only way you would ever be convinced is to try them.
I hope this answers your questions.
