Hello,

Volvo’s new S60 AWD uses the Haldex system and the up coming XC 90 will have the same type of AWD system that is used in the S60 AWD. I have also heard that the current V70XC will have its AWD system replaced with the Haldex system late this model year.

Haldex is a Swedish company (http://www.haldex.com/index_main.asp) that designs and manufactures an electronically controlled hydraulic clutch. This electronically controlled hydraulic clutch will replace the current viscous coupling that is currently being used in the current and past V70 XC. The advantage of having an electronically controlled hydraulic clutch over a viscous coupling is that the hydraulic clutch can disengaged the front wheels from the rear wheels. This will eliminate the wheel binding that can occur when different size tires are used on the front verses the rear (like a spare tire). However, there still is a problem. If you do not maintain the tire size the same strict way that the current viscous coupling tire size is maintain then the hydraulic clutch will never engage hence you have an AWD drive car with out AWD.

There are several car companies that are currently using an electronically controlled hydraulic clutch. Some of them are VW Passat 4 Motion, GM Buick Rendezvous, Acura MDX just to name a few.

Anyway that is what I have been able to figure out up to now.

Good luck,

Steven---