Scotty, absolutely love the channel! Thanks for sharing the all information and experiences that have taken you lifetime to accumulate. I am buying a sprinter van with the intent of converting it into a camper. Could you please share your insights on 4wd vs AWD? Cheers!
Sounds like it's an automatic active part time system.
It's 2WD by default and automatically engages the front axle when needed.
Since the torque split is variable, it means it will handle better than a manual part time 4WD drivetrain.
In terms of ownership and upkeep, both are added costs and complexities. Manual systems require more skills on the part of the driver to operate, whereas automatic systems are designed to be seamless on/offroad with minimal input from the driver. Refer to the owner's manual for specifics on how and when to use it and what not to do.
All 4WD/AWD drivetrains will hurt your fuel economy by 1 or 2 mpg, unless it has a locking hub feature which I don't think the Sprinter has.
This being a Mercedes, I guarantee there will be additional sensors and computer modules to make their system work, which can make repairs more costly and complicated to diagnose. Will your neighbourhood mechanic know how to work on it? ... probably not.
There's no specific definition, it's up to the manufacturer how their system is marketed. The AMC Eagles I've owned were marketed and badged as "4WD" despite having full-time "all-wheel-drive" systems. My 1999 Jeep Cherokee is also badged "4WD" and that has a part-time system which cannot be used on dry pavement. So really the only way to know for sure is to check the vehicle specifications.
They are kind of "catch-all" terms mostly used for marketing. You'll have to read the product literature about the specifics, since every AWD/4WD system works differently.
But generally speaking...
4WD is part time. You normally drive in 2WD and then engage 4WD when you need it.
AWD is meant to be used all the time. On and off road.
This is a tough one to answer simply, because there are so many variations. Both basically engage all four wheels. It is just a matter of how it does it and when it does it.
4WD usually requires user engagement. And it is usually engaged only when you need four wheel drive, like when on trail or off roading. It is not usually smart to use 4WD like you would for normal driving (freeways or city). Otherwise you intentionally stay in 2WD. There is usually a shifter, lever, or knob to engage 4WD, and in older cases, you actually have to get out of the car and engage the wheels physically yourself
AWD doesn’t usually require user engagement. The car just knows how to distribute power between all four wheels. And AWD is on all the time. Depending on the specific car, AWD can be used for freeways and city, but not all AWD can be used for trails and off-roading.
There is one anomaly AWD vehicle, the RAV4 hybrid. In many ways, it is like a 4WD vehicle because most of the time it is just two sets of wheels powering the vehicle. In a RAV4 hybrid it is the front two wheels. In most 4WD, it is usually the rear two wheels. But the RAV4 hybrid basically has them completely off. AWD only gets activated on launches, and on trails / off-roading. But the reason it is considered AWD even if it is 2WD most of the time is because the user doesn’t have to do anything. The car just knows.
I drive a Jeep Patriot with AWD. There's important things to know about owning an AWD vehicle so you don't accidentally burn up the clutch packs in the AWD drivetrain.
The main difference between 4WD and AWD is the coupling units used in AWD instead of transfer cases used in 4WD. Inside the AWD coupling units are clutch packs which are similar to the clutch packs used inside automatic transmissions. When the AWD clutch pack is compressed together and engaged, power is sent to the wheel through that clutch pack. If the clutch pack is disengaged then the clutch discs can spin freely and no power is sent to the wheel.
What causes the AWD clutch packs to overheat and burn up is when there's a difference in tire rotation speed between the front and rear tires. If the front tires are rotating faster than the rear tires that causes half the clutch discs to rotate at a different speed than the other half of the discs causing friction between the clutch discs which leads to the clutch discs overheating. Half of the discs are connected to the front wheels and the other half connected to the rear wheels. In the diagram above the front wheels would be the blue discs and rear wheels the red discs.
This is the reason Scotty always says all four tires need to be replaced at the same time on an AWD vehicle so all tires are the exact same size and turning at the same speed. It's also important to rotate the tires from front to back every 5,000 miles so the tires wear evenly and remain the same size.
3D animation showing Audi's AWD systems. Notice how they all use clutch packs.
AWD vehicles need to be towed on flatbed tow trucks. If a flatbed truck isn't available and a wheel lift tow truck shows up instead, then dollies must be used so there's no tires left touching the ground while towing. Lifting the front wheels and leaving the rear wheels on the ground will instantly burn up the AWD coupling unit's clutch pack because half the clutch pack discs will be spinning with the rear wheels and the other half will be completely stationary with the front wheels. Causing massive friction and heat between the clutch pack discs inside the AWD coupling unit!
I'm extremely nervous about using small spare tires on an AWD vehicle. Since the spare tire isn't the same size as the other tires it will cause the clutch pack discs inside the AWD coupling unit to spin at different speeds and overheat.
The AWD Jeep Patriot comes with a donut tire. If I ever used it I'd drive 15MPH to the nearest tire shop and hope there's no damage to the AWD clutch pack. I'm surprised a spare tire is even included in AWD vehicles considering how much damage it can cause. Before I knew how AWD systems worked, I would have slapped that spare tire on and drove 60MPH down the interstate.
@oskool Not all AWD systems have clutches. Some, like mine, have a viscous coupling. The Sprinter appears to have clutches though. Since it's electronic, you may be able to pull out the AWD fuse, should you need to use a compact spare for extended periods of time, to prevent AWD activation. But for short trips, I think it would be OK. When you think about it, using a slightly different tire is the same as taking a gentle turn. I think you'll only see damage over a long period of time. But again, specifics need to be gleaned from the operating manual.