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Discussion Starter · #1 ·
Over the weekend I had all 3 of my XC90s up on the lift and I noticed a few differences.

My XCs are 2005, 2008 and 2010. All 3 have different rear differential controllers also known as Haldex couplers.

The 2005 has a very skinny looking system with side mounted steel cap for the oil filter.


The 2008 has similar but different system. It seems to be more bulky with larger drive shaft attachment.


And my 2010 has a top mounted filter impossible to reach for replacement. Also the system is the largest of all.




So I think that there must be at least 3 versions of the Haldex systems used in that 5 year stretch.

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Yes, Haldex evolved at least 3 times throughout those XC90 model years; Instant Traction was also not available in the early XC90 model years.
 

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Discussion Starter · #3 ·
So would it be safe to say that we have Halsey Gen 2, Gen 3 and Gen 4 in there?


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So would it be safe to say that we have Halsey Gen 2, Gen 3 and Gen 4 in there?

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Yes, it'd be right to say so.
This is what came on my 13 2.5T XC90.
Looks like Haldex 4
 

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Discussion Starter · #7 ·
On further inspection for whatever reason the 2005 and 2008 look identical although in person the housing looked a lot smaller so I cant figure out of if that was early GEN 3 with a steel filter cover vs the 2008's Aluminum cover with fins. In the end I think they may be the same but the drive shaft coupling is different so there seems to be quite a few differences even though they look somewhat the same.
 

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Yup, they're both gen IIIs even if the prop shaft and connector thing which I lost the word for might be different for what ever reason. I know because I also have a gen III haldex on my 2007 Volvo and it had the old steel filter cover until I did a filter change, the new finned cover was included in the filter kit. Don't know what different it makes though, wouldn't have imagined the filter cover would need to dissipate a lot of heat?
 

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Discussion Starter · #9 ·
Now looking at some pictures of my old V50 which was a GEN 2 as they never got GEN3 on that model at least not until much later, my 2005 looks just like my GEN2 2006 V50. I will post some pics to compare.
 

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So, let me get this right... the early V8s have Gen 3, but also have "instant traction" from what I've seen. The Gen 4 is supposed to be immediate engagement, so does that mean a Gen 4 V8 has instant-er traction? LOL
 

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Discussion Starter · #11 ·
I think based on what I saw is the first V8 in 2005 had gen 2.


This is what is on my 2005. This includes 2003-2005 all engine versions.

Then 2006 sometime they get Gen3


Then 2009 they move to gen4


You can see gen3 vs gen4 side mounted filter vs top mounted filter. The gen2 is way smaller than the 3.


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Discussion Starter · #12 ·
So, let me get this right... the early V8s have Gen 3, but also have "instant traction" from what I've seen. The Gen 4 is supposed to be immediate engagement, so does that mean a Gen 4 V8 has instant-er traction? LOL
I think the main difference between the GEN3 and GEN4 is that GEN3 had 2 pumps, mechanical and electrical, then GEN4 got rid of the mechanical one relying only on the electic pump for pressure.

In that same category im not sure if GEN2 only had mechanical pump, which would explain the dealy in engagement to the rear wheels. So in that sence, yes I think GEN2 (Slow), GEN3 (faster engagement), GEN4 (fastest engagement), although probably not much difference between 3 and 4, at least not noticeble to the driver.
 

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Discussion Starter · #13 ·
Found this info online as well. More or less what we know about them.

Second generation - 2002

The second generation of Haldex coupling is an electronically controlled permanent 4x4 system with a Haldex differential calculating how much drive should be directed to the rear wheels. The Haldex system automatically distributes power between the front and rear wheels depending on slippage, but normally sends 95% of the power to the front wheels. It can react in as little as one seventh of a revolution of any wheel. Power transfer in the second generation is much more effective. Electronic sensors and controls can modify the system's response characteristics, for better operation in conditions ranging from dry pavement to loose gravel, snow, ice, or mud. A pre-charge pump charges the hydraulic system to allow the coupling to engage quickly. This pump is improved again for the third generation to allow for greater speed.

Third generation - 2006

The third generation of Haldex coupling made its appearance on the newly re-designed Land Rover Freelander 2 (LR2 in the United States). With enhanced capabilities, it allows more immediate off road response. The Freelander's 4x4 system has been developed in conjunction with Haldex, whose centre-coupling technology continuously alters the front-rear torque split, normally through a hydraulically operated multi-plate wet clutch. However, Land Rover wanted an electronically controlled centre coupling – linking the propshaft to the rear differential – that could pre-engage at rest to reduce wheelspin from standing starts, engage quickly when traction loss was detected and disengage quickly without compromising stability control systems. The system also had to transmit the necessary torque to achieve Freelander 2's off-road traction demands. The result is used exclusively on Freelander 2, and pre-emptively engages four-wheel drive quickly and completely. An improved high-pressure pre-charge pump charges the hydraulic system as soon as the engine is started, allowing for full-time 4x4 from rest. It also reduces the time taken to achieve full torque once wheel-slip has been detected – within 15 degrees of wheel-slip rotation (compared with 50 degrees of wheel-slip rotation with the previous generation Haldex). The Freelander 2's Haldex unit is designed to allow up to 1500 Nm of torque transmission. An accumulator also speeds up the unit's response. Full torque transmission can be achieved in 150 milliseconds. In effect, the new Haldex coupling gives the benefits of full-time 4x4 and the efficiency and fuel economy of an on-demand system.

This generation of Haldex coupling is later shared with Volvo's complete lineup (Manufactured 2005-2008, depending on model) and is called "Instant Traction" in documentation by Volvo.

Fourth generation - 2007

Saab introduced a unique combination of Haldex Couplings on its 9-3 Turbo-X in late 2007. Called XWD (Cross-Wheel Drive), it allowed enhanced traction, safer driving, and better control. The main components of the new Haldex system are the Power Take-Off Unit (PTU), Limited Slip Coupling (LSC) and eLSD (Electronic Limited Slip Differential). The PTU is the final drive unit at the front of the vehicle that transmits power to the front wheels and sends power down the driveshaft to the rear wheels. It is not a Haldex design, but is required to adapt the system to a front-wheel drive vehicle. The LSC sits at the rear of the vehicle in-line with the driveshaft. It controls the torque split between the front and rear wheels of the vehicle. The LSC sends torque to the eLSD that sits between the rear wheels. The eLSD transfers torque to the two rear wheels. Like with XWD, previous generation Haldex systems also included an LSC and an LSD. However, with the new system Haldex significantly redesigned the workings of their LSC. The LSC is still a clutch pack that adjusts torque split depending on hydraulic pressure. It is the method of fluid flow through the device that has changed.

A large complaint about the old system was its lagging response time. LSC versions 3.0 and earlier used a built-in pump to create hydraulic pressure on the clutch pack to increase the torque drive to the rear wheels. While efforts were made on Haldex's part to create pre-emptive torque by adding a check valve and feeder pump to provide some instant pressure when triggered by wheel slippage, it was still limited in capacity. That is why for version 4.0 Haldex made an effort to improve response time by eliminating the hydraulic pump built in to the LSC, which also reduced its overall packaging size. Instead they have added a proportional pressure release valve with an accumulator that is kept filled by a detached feeder pump. This provides more instant response by holding the valve open to limit the torque drive to the rear wheels and keeping the hydraulic fluid flowing through the system. That way when rear torque is demanded, the valve closes and hydraulic pressure is already there.

The LSD used by Haldex 4.0 is also not the mechanical limited-slip differential of old. They swapped the old system LSD for an electronic unit. The eLSD works in much the same way as the LSC, a feeder pump and pressure relief valve are used to control hydraulic pressure on the differential clutch pack. This allows for complete control of the rear differential lock-up without the need to wait for wheel slippage to occur. The system has its own control unit contained in the LSC. This control unit communicates between the vehicle systems to get sensor input for data such as wheel speed, rpms, throttle position, steering wheel input, etc. It also works with anti-lock brake and traction control systems.

The XWD system can transmit 100 percent of available torque to either the front or rear wheels. However, for those conditions to occur one end of the vehicle would have to lose all traction, like driving on ice for instance. During a standing start the rear wheels are put to use, without the need for any slip to occur. Then under straight-line cruising conditions, to conserve fuel and driveline wear, the torque split to the rear wheels is reduced to a level between 5 and 10 percent. Also up to 85 percent of torque can be transferred by the eLSD between to any single rear wheel if necessary. The system can adjust torque splits based on calculated conditions, such as those that indicate an aggressive lane change manoeuvre, to effectively reduce oversteer or understeer without any wheel slip occurring. In the event that some wheel slip does actually get to occur, the system can react more timely and efficiently than in the past.

Thanks to this technology, the Saab 9-3 Turbo-X, with only 280 bhp (210 kW) can run a slalom faster than many high performance sports cars, beating German and Japanese rivals. Saab has an agreement with Haldex for exclusive first year access to the technology, and use of the "XWD" trademark. Haldex is currently developing a similar AWD system for Hyundai Applications.
 

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This thread motivated me to have a peek at my non-US 2008 XC90 2.5T. I gather I have a Gen III then?

Auto part Automotive wheel system Rim Wheel Vehicle

Auto part
 

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Discussion Starter · #15 ·
This thread motivated me to have a peek at my non-US 2008 XC90 2.5T. I gather I have a Gen III then?

View attachment 17402

View attachment 17410
Yes, the side cover (Aluminum wiht fins) with that housing is certainly GEN3.
GEN2 is probably present on 2003, 2004 and 2005s. I doubt 2006 would ever have it but its possible on say models like the 2.5T and the T6.
 

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Gen III was the first to have instant traction if I recall correctly. Gen IV however uses an accumulator tank which can build up pressure in advance and essentially dump the clutch by the opening of a valve. Gen III needs to build up pressure by pumping. I think both III and IV have the "passive" mechanical pumping provided by the prop shaft being turned (by some rollers and internal trickery that I don't fully understand) and that gen V is the first to rely solely on the electrical pump (edit: nope, gen IV seems to not have mechanical pumping)

Also, as I said, the cover for the filter isn't a definite tell as to which generation the haldex is. My gen III had the thin flat lid but now has the finned one provided in the filter it. The location of the filter itself on the coupling (relative to the pump, prop shaft etc) is however a good way to tell which generation it is.

For what it's worth, part numbers for the AOCs seem to differ between models in VIDA. But I looked up a 2005 V50 AWD and searched that part no and it returned results for S40 and V50 cars between 2005-2010 (I guess gen IV never made it there). The part no for my 2007 S80 returned results for 2007-2008 S80s as well as V-/XC70 2008 (2009 was first to have gen IV). And lastly I searched the haldex part no for a 2005 XC90 V8, which returned results for 2005-2008 XC90s.
 

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Long time lurker and first time poster here. I have an 07 XC90 3.2 that has been relatively problem free and has just turned over 190k km. Trying to diagnose a possible Haldex DEM or AOC pump issue and was wondering if you guys know if it’s posisble to remove the AOC pumps on the Generation 3 system without having to remove the drive shaft. I got an Autel scanner although now after reading more I wish I had gotten a Vida/Dice device. I will eventually end up trying to see if the pump has power going to it but was wondering if it can be removed with the drive shaft in place.
 

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I'm no expert on this, but I do believe there is nothing else holding the driveshaft at the rear end. If you're planning to keep it off the road until you replace the unit, it could be possible.
 

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The only issue I can think of is that there isn’t enough clearance between the pump assembly and the prop shaft flange. On different generations the pump has a metal nipple that sticks out and people seem to sand it down just enough to be able to remove the pump with the drive shaft in place.
 

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AFAIK it's not possible to remove the pump on gen III without dropping the prop shaft.
 
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