All-wheel-drive system is a somewhat complicated topic. The main factor lies in: there are many types of differential, and also an AWD system always has 3 differentials (front/center/rear), hence there are many possible combinations of ways to implement an AWD system.
Since a typical consumer may not have enough knowledge to understand all technical details behind the AWD system, automobile manufacturers usually employ a single, unified generic term to name all of its AWD systems. Take Volkswagen as example: all of its AWD systems have only one name: “4Motion”, the same thing applies to Audi’s Quattro system.
The current way that car makers name their AWD products seems to be user-friendly from consumer’s aspect. However the downside is: most buyers may not fully understand what they have purchased, and also what is the actual capability of the AWD system on their cars.
The Volkswagen Touareg is a perfect example of such marketing conduct. Many people know Touareg has a 4Motion AWD system. But in fact the truth is: there are different types of AWD implementation behind the “4Motion” nameplate. This means your Touareg 4Motion may be dramatically different than other people’s Touareg 4Motion. In this article I will try to provide the most comprehensive and accurate review of all 4Motion systems within the Touareg product line.
As of the time when this article is written, Volkswagen has a total of 2 generations of Touareg. Let’s take a look one by one.
First Generation Touareg
The 1st generation Touareg (internal code: 7L) is produced between 2002 and 2010. The below #1 and #2 descriptions are for the 1st-gen Touareg:
1. 1st-gen Touareg 4Motion: it uses a planetary gear-set center differential, plus an electronically controlled, multi-plate clutch as the limited slip mechanism. It also has a low range gear. The center differential is manually lockable and this comes as a standard feature; in addition, you can also opt for the optional rear differential lock;
2. The DEFAULT front:rear power split ratio of the planetary gear-set center differential is 38:62, determined by the physical gear ratio. However, VW implemented an “always on” command into the multi-plate clutch control ECU program, which forces the limited slip to be always kicked in, which is sending an extra of 12% of torque to the front wheels by default. This effectively makes the final system power split ratio to be 50:50 under normal driving conditions.
The reason why Volkswagen did this was mainly due to the fact that Touareg is sharing its platform and some of the powertrain components with the Porsche Cayenne. Porsche wanted the front/rear power split to be 38:62 on Cayenne, while VW wanted it to be 50:50 on Touareg, and they do not want to design and produce two physically different center differentials (in order to lower the cost). Therefore, Volkswagen came out with this workaround, which uses a mechanical 38:62 center differential, and then tunes it to 50:50 within the software layer.
Because of this “always on” setting on the 1st-gen Touareg limited-slip clutch, the electric motor that operats the clutch pack is under heavy workload constantly, which leads to premature wear. It has been reported by some users that their 1st-gen Touareg need to replace the electric motor every 2-3 years.
Above image: full view of the AWD system of the 1st-gen Touareg (2003 model year shown)
Above image: transfer case of the 1st-gen Touareg, containing the planetary gear-set center differential, the multi-plate limited slip clutch and also the low range gear.
Above image: AWD mode selection knob on the 1st-gen Touareg
Above image: AWD status display on the 1st-gen Touareg
Second Generation Touareg
The 2nd generation Touareg (internal code: 7P5) is produced since 2011. In this generation, things become more complicated than before. The below #3 to #6 descriptions are for the 2nd-gen Touareg:
3. For non-US markets, there are two types of 4Motion system on Touareg. One is called “4Motion” and another is called “4XMotion” (in some markets, it is also called “4Motion Terrain Tech”);
4. 4Motion on 2nd-gen Touareg: it uses a TORSEN Type C center differential, 40:60 default front/rear torque split, it does not has the manual full locking feature; also rear locking differential is unavailable. Rear wheel limited slip is implemented through ABS;
5. 4XMotion on 2nd-gen Touareg: it is the same as the 4Motion in 1st-gen Touareg with the locking rear differential option;
6. In US market, VW does not sell the 4XMotion. All 2nd-gen Touaregs sold in US is the 4Motion mentioned in the above point #4.
Above image: full view of the AWD system of the 2st-gen Touareg (2015 model year shown)
Discussion and Summary
The 2nd-gen Touareg 4Motion has weaker off-road capability than the 4XMotion version, but it has two major advantages: (a) TORSEN center differential has a lighter weight; (b) it can mechanically detect the tendency of slipping, and even react immediately before the slipping has actually occurred; in other words: TORSEN differential can PREVENT slippage. This is extremely useful when driving in the snowy road surfaces, which can be considered to be the most common use case that a typical US consumer will face.
The 4XMotion system has the advantage of handling serious off-road situations, thanks to its 100% locakable center/rear differential (in theory the TORSEN differential cannot achieve full lockup by itself). Of course, the disadvantages are mainly in the heavier weight and more expensive manufacturing costs.
It is hard to say which one is better. My personal opinion is: the 4Motion (TORSEN based) is suitable on paved roads, and is better at high speed driving on snowy or wet road surfaces; the 4XMotion is more suitable in places where maximum traction is absolutely required (for example driving on sands, desert, swamp etc.)
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