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How does the Haldex AWD work?

23K views 9 replies 7 participants last post by  Calhon 
#1 ·
Mj__Smith's question concerning his Haldex got me thinking. How does Volvo's Haldex system actually work? I mean mechanically. With the ABS system? Clutch pac? If so, is it electronically or fluid activated? What does it take to engage the rear wheels? How much slippage or is it a true AWD system? Are the rear wheels along for the ride unless needed?

Can torque be transferred between the rear wheels (side to side)? How is this done? Between the fronts?

Several years ago the Haldex systems was suppose to be improved. What, exactly, did that mean? Quicker engagement? How?

I understand 4x4 and AWD systems in general, but not Volvo's system. I'd like a 101 primer, or a place to look for the answer. Thanks.
 
#3 ·
Re: How does the Haldex AWD work? (GrecianVolvo)

Quote, originally posted by GrecianVolvo »
http://www.billswebspace.com/HALDEX.pdf

That's interesting reading. Thanks for posting it Yannis. So, I'm puzzled about something. If the Haldex guide (the pdf file) has a "Mr Exclamation" icon on page 3 indicating how important it is to change the oil and filter in the unit every 20k miles, why doesn't Volvo indicate this in it's scheduled maintenance ?
 
#5 ·
Re: How does the Haldex AWD work? (safetyfirst)

Quote, originally posted by safetyfirst »


That's interesting reading. Thanks for posting it Yannis. So, I'm puzzled about something. If the Haldex guide (the pdf file) has a "Mr Exclamation" icon on page 3 indicating how important it is to change the oil and filter in the unit every 20k miles, why doesn't Volvo indicate this in it's scheduled maintenance ?

That is not an OFFICIAL page...I am not sure and every manufacturer has tailored Haldex to their own needs, etc. I did not have the time to look for anything more official.
 
#6 ·
Re: How does the Haldex AWD work? (GrecianVolvo)

I used to own an Audi TT quattro, and it did require the a Haldex service every 20K miles. The pdf above mentioned uses a graphic of a TT so I believe that service reference is based on the first generation of TTs. I also have an A4 but no Haldex service is needed either. So again I guess that reference was only written based on the TT haldex application and it doesn't apply for all haldex systems.
 
#8 ·
Re: How does the Haldex AWD work? (Asfalto)

The PDF describes Haldex gen I, which launched on the first generation Audi TT. Generation II (launched with the XC90) and later Haldex couplings require no oil or filter change. New Volvos use the latest Haldex gen IV units.
 
#9 ·
Re: How does the Haldex AWD work? (Calhon)

Quote, originally posted by Calhon »
The PDF describes Haldex gen I, which launched on the first generation Audi TT. Generation II (launched with the XC90) and later Haldex couplings require no oil or filter change. New Volvos use the latest Haldex gen IV units.


I believe that only the XC60 uses a 4th generation Haldex. Rest of cars use 3rd generation.
 
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