The Haldex system gets its name from the Haldex coupling, which rally racer Sigvard “Sigge” Johansson invented and subsequently sold to the business that now sells similar AWD systems to VW/Audi for use in cars. When the front wheels lose traction, the Haldex system enables front-wheel-drive automobiles to transfer power to their rear wheels. The Haldex unit engages a clutch that sends power to the back wheels, giving the vehicle momentary all-wheel drive. This configuration varies from other AWD systems in that it only serves as a support system and not the primary source of AWD. Instead of a full-time AWD system like Audi’s Quattro or Subaru’s Symmetrical AWD, every car with a Haldex system has a front-wheel-drive configuration that can send power to the rear wheels under certain circumstances.
Although from a marketing standpoint VW refers to its AWD systems as “4Motion,” the system is actually a Haldex unit and does not provide full-time AWD. Similar to this, certain Audi systems branded “Quattro” are actually Haldex-based Haldex drive systems rather than genuine Quattro drive systems. Most notably, while dubbing the AWD “Quattro,” the 8P A3’s drivetrain is identical to that of the MK5 R32. When and how much power should be applied to the rear wheels is determined by the Haldex AWD using the ECU systems that monitor traction at the wheels. The ECU hydraulically engages clutches through the connection when it detects the front wheels slipping, whether it is during a forceful launch, a corner, or bad traction circumstances. This sends power to the back wheels. There are currently 5 generations of Haldex systems that are frequently found on platforms from VW and Audi, which we have mentioned below.
Officially released and used in the Audi MK1 TT and VW MK4 R32 was the first generation of the Haldex we are familiar with today. This device can bias power from a 90-10 front to rear distribution to a 50/50 power distribution in less than half of a wheel rotation while operating in high slip situations, such as launches in bad weather. For Gen 1 Haldex systems to function properly, routine fluid and filter changes are necessary.
The Audi MK2 TT, Audi 8P A3, and VW MK5 R32 all feature the second generation Haldex system. When servicing, this system also has to have its filter changed because it is reactive. A small improvement over the Gen 1 Haldex System, Gen 2 systems also bias power from 90-10 to 50-50 in a quarter wheel revolution of slippage.
The first system that was proactive rather than reactive was of this generation. The Gen 3 system has the ability to power the rear differential prior to any front slide and maintain preloaded tension on the clutch packs in the rear differential. Sadly, no Audi or VW model had this system in North American markets, but if you drive a Volvo or Land Rover, your car may have a Gen 3 Haldex that likewise needs a filter replacement when maintenance is due.
The most ambiguous generation in terms of models with a Gen 4 Haldex is this system, which is the last to use a filter. This technology is included in the VW MK6 R up to 2014, although the Gen 5 system is present in Tiguans starting in 2012. The best way to confirm whether your car has a Haldex system with or without a filter is to use the VIN. Passats from this era are no different.
The little screen pump can be removed during service and ought to be cleaned before your service is finished because this is the first Haldex system without an integrated filter. After you have taken the screen off and cleaned off any debris, you can easily reattach it with two little screws. Make sure to check your VIN or get in touch with our sales staff to find out if your 2012 model-year VW or Audi has this technology installed.
As simple as changing your oil is, you can service your Haldex. Basic hand tools, a fill tool like our Schwaben Fluid Pump to fill the system, Haldex gear oil, fill and drain plugs, and a Haldex filter if you have a Gen 1-4 Haldex are all necessary for servicing your Haldex. Once the fluid and filter (as necessary) have been replaced, the Haldex service must also be finished. This needs a relearning procedure. You must have access to VCDS with VAGCOM or ask about it at your nearby VW shop in order to complete the relearn procedure.
1: To find out what systems are installed on a car made after 2012, physically check your Haldex unit or get in touch with our sales team with your VIN. You have a Gen 4 system with a filter if your Haldex resembles the one on the left. A Gen 5 system without a filter is what you have if it resembles the one on the right.
2: You’ll need standard hand tools for working on German cars, an Assembled by ECS Haldex Service Kit, a Schwaben fluid pump tool to fill the system after it’s been drained, and a filter to finish the service (Gen 1-4). While our Schwaben Haldex 90 Degree Adapter Kit aids in reaching into tight locations for the most convenient Haldex service, the Schwaben Haldex Oil Filter Wrench can make your life easier while replacing the rear differential filter.
3: To drain as much fluid as possible from the Haldex drain plug, raise the vehicle in the air and make sure it is level front to back, or slightly lower in the back.
4: Take out the filter and fill plug. Before installing the drain plug and the new filter, replace the old one and torque them both to specifications. There isn’t a “serviceable filter” on Gen 5 vehicles, but there is a screen that is attached to the Haldex pump that we advise you to take out, clean, and then reinstall. If you decide to do this, take caution when removing and replacing the screws on the screen because neither VW nor Audi sells this screen separately. After cleaning, cautiously reattach the Haldex pump and huge screen.
5: Fill the system with fluid through the fill plug until it comes out of the fill hole, insert the fill plug, and tighten the plug to specifications to complete the process.
You have now successfully serviced your Haldex! Please feel free to contact any of our skilled Sales Representatives or Technical Service Advisors with any queries you may have. We will be pleased to address any worries you may have with your VAG car and Haldex system. Our inventory of VW parts and Audi parts is prepared to assist you with your next do-it-yourself project for any other maintenance you may require.
In This Article...
Audi employs Haldex?
The viscous coupling was replaced with the SwedishHaldex Traction LSC unit beginning in 1998. Audi’s quattro models of the Audi S1, Audi A3, Audi S3, and Audi TT all include Haldex. Additionally, it is utilized by Volkswagen in the 6th generation VW Passat (also built on the A-platform), Transporter T5, and 4motion versions of the Mk4 and Mk5 generations of the Volkswagen Golf, Jetta, and Golf R32. The Volkswagens get the moniker 4motion, although the trademark on the Audis still stands and they are still referred to as quattro. Based on Volkswagen Group cars, the Koda Octavia 4×4, SEAT Len 4, and SEAT Alhambra 4 all utilized Haldex LSC. Curiously, the Bugatti Veyron also uses Haldex, but with a different PTU, front and rear axles, and transmission.
A pseudo-center differential is created by the Haldex Traction LSC multi-plate clutch with electronic control from the ECU.
How: A front-wheel drive car is the norm. Depending on the situation, a Haldex Traction LSC unit may direct up to 100 percent of the torque to the rear axle. The torque distribution on Haldex Traction devices often confuses people. The Haldex LSC clutch functions at 5% under typical operating circumstances (divide 5 percent between front and rear, and 97.5 percent torque goes to the front, and 2.5 percent goes to the rear). The Haldex clutch has the ability to lock with a 100 percent clamping force under challenging circumstances where both front wheels lose traction. This means that all torque (less losses) must be delivered to the rear axle since no torque is transferred to the front axle. With a typical open differential, the torque is divided between the left and right wheels. The Electronic Differential Lock (EDL) regulates if one driving axle side loses traction. EDL only brakes one rotating wheel; as a result, torque is distributed to the other wheel via the open differential. The EDL solely manages the front wheels on all transverse-engined vehicles with the Haldex Traction LSC four-wheel drive system.
If both the front and one of the rear wheels lose traction, the car will not move in vehicles having EDL on the front wheels alone.
In off-road circumstances, it just takes for one front and one rear wheel to lose traction for the car to become immobile due to the restrictions of Electronic Differential Lock (see quattro IV description above).
Since there must be a discrepancy in slip (or rotational speed) between the two axle systems before the Haldex Traction system activates and distributes torque to the rear axle, it is more reactive than preventative. As the system can respond in less than the full revolution of any wheel on the vehicle, this is not the same as wheel spin. Slipping is less likely to begin thanks to the Torsen’s constant, “full-time” even torque distribution under no-slipping situations.
As soon as brakes are applied, the Haldex Electronic Control Unit (ECU) disengages the Haldex clutch in the center coupling, enabling ABS to function effectively. The clutch is removed by the electronic control unit when making small, slow turns (like parking), preventing “wind-up” in the transmission. The Haldex is removed when the Electronic Stability Programs (ESP) are active, allowing the ESP system to efficiently regulate the vehicle during acceleration and deceleration.
Audi started utilizing Haldex when?
initial generation 1998 The Haldex Coupling made its debut with an electronically controlled hydraulic-mechanical all-wheel drive concept in the Audi TT, Audi S3 8L, and VW Golf. When the front wheels start to slip, this mechanism makes an effort to engage the rear wheels.
Is Haldex AWD reliable?
As the phrase goes, we were all created equally, yet some of us are more equal than others. The same might be said of all-wheel drive systems, but is Subaru’s Symmetrical All-Wheel Drive superior to Audi’s quattro? It’s possible that this debate will never be resolved. However, there are certain AWD systems that aren’t exactly real, pure, or often even what they’re branded as (mainly Haldex).
You may or may not be familiar with Haldex AWD, but I can almost promise that you have heard of several of its uses, including the Volvo S60 T6, Mercedes-Benz A45 AMG, Volkswagen Golf R, Audi S3, and RS3. But wait, don’t they use quattro, 4Motion, 4MATIC, and so forth? Mercedes-Benz, for example. These names are simply what each automaker chose to call their AWD drivetrains. In order to avoid any confusion, what is Haldex?
For many years, the Swedish manufacturer HaldexAB, which is now owned by BorgWarner, has specialized in producing all-wheel drive systems evolved from front-wheel drive configurations. Haldex 4WD typically transforms a front-wheel drive (FWD) platform into an all-wheel drive (AWD) system by using electronic sensors and differentials to send power to the rear wheels, such as those seen on the VW Golf, Audi A3, or Mercedes-Benz A Class.
Haldex AWD is not truly “true” all-wheel drive, to be clear. Drivetrains that permanently drive all four wheels are referred to as AWD systems. Due to traction loss or other factors, these systems may distribute more torque to wheels with more traction, sometimes even up to 100% of the torque, temporarily leaving some wheels undriven. However, their default configuration drives all four wheels of the vehicle.
Haldex is therefore a four-wheel drive system rather than an all-wheel drive system (4WD). Since Haldex is built on transverse-mounted FWD systems, Haldex AWD only drives the front wheels by default. The Haldex computer systems shift torque to the rear wheels when wheel-slippage is detected in order to make up for the front wheels’ loss of grip. A Haldex-equipped vehicle will typically steer power rearwards during acceleration to increase traction, but under normal driving conditions, front-wheel drive will be the only mode of operation.
Haldex does have a number of advantages, especially for enterprises with restricted development expenditures. Manufacturers don’t have to spend millions of Rands, Dollars, or Euros creating and studying all-wheel drive systems because Haldex is an outside corporation that sells and equips products to automobiles. Since practically all front-wheel drive (FWD) vehicles may be upgraded with Haldex systems, FWD is widely used as the standard drive system by numerous manufacturers. Haldex also offers better fuel economy because it typically only uses the vehicle’s 2 wheels, switching to the 4WD only when additional traction is needed.
The Haldex AWD system has advantages and disadvantages, much like any other system. Due to Haldex’s predominately front-wheel drive design, under heavy loads, Haldex-equipped vehicles have a propensity to understeer significantly because the computers frequently take too long to distribute torque to the rear axle and because the front-wheel orientation of the system’s default torque distribution. This was a common issue with cars like the Audi RS3, which was notorious for its persistent understeer that was frequently and wrongly attributed to the quattro system of Audi.
Haldex AWD’s most recent iteration has made some progress in decreasing understeer, although the system’s final tuning by the system’s makers is mostly responsible for this. For instance, Audi and VW modified the Haldex system in the S3 and Golf R to anticipate the driver and to briefly shift 100 percent of the torque to the rear axle, enabling oversteer. However, Mercedes-Benz only configured the A45 AMG’s Haldex to be able to deliver 50% of its power to the rear, making the car more prone to understeer, a characteristic of Haldex.
Haldex cannot ever be a permanent AWD system that has been adequately built. Since AWD systems are designed from the ground up to function as AWD, many of the drawbacks of FWD-based arrangements are eliminated. Haldex offers a more affordable option to creating a true all-wheel drive (AWD) system, however it cannot and will not be able to perform in the same manner because it will always operate as a front-wheel drive system.
Haldex nevertheless demonstrates to be a sophisticated device. In contrast to genuine AWD systems, which demand a very high level of driver skill to handle and steer the vehicle on or over the limit, it responds in a way that flatters the driver and frequently helps them to recover from difficult situations without much trouble. Haldex is a secure substitute for permanent AWD for the typical driver as a result.
Haldex is an AWD system based on front-wheel drive, but there are several outliers. The Bugatti Veyron and Lamborghini Avantador are both categorized as having permanent all-wheel drive, however if one digs deep enough, they both use Haldex. The front-wheel drive systems in the Aventador and Veyron were not “reversed” to predominantly drive the rear wheels, nor were they designed as front-wheel drive vehicles. Instead, to distribute and apportion torque across all 4 wheels, modern vehicles use Haldex-based electronic locking differentials, however under normal conditions all 4 wheels are permanently driven.
Conclusion:
Haldex AWD is a front-biased arrangement, with the exception of the Bugatti Veyron and Lamborghini Aventador. Because the AWD systems in the Audi RS3 and Mercedes-Benz A45 AMG are truly front-wheel drive biased, they cannot be blamed for the Audi RS3’s and Mercedes-Benz A45 AMG’s tendency to understeer. All all-wheel drive systems may be considered equal on a daily basis, however in extreme conditions, permanent all-wheel drive systems like quattro and Symmetrical All-Wheel Drive are actually more equal than others.