My vehicle is a 2009 T6 and is fitted with a Series 3 Haldex Unit. Volvo does not identify this as a component that requires servicing, yet other vehicle manufacturers have recommended service intervals.
A few facts:
Availabilty of replacement Haldex Fluid (P/No 31367941) from Volvo is very restricted and expensive.
Recognised lubricant manufacturers dont have an equivalent substitute product despite AUDI, VOLKSWAGEN, SEAT, SKODA, OPEL, LANDROVER and VOLVO vehicles all using this fluid in their Haldex Units.
Research will find there is an alternative to the vehicle manufacturers products, which all come with a variety of premium price tags.
I was fortunate via a semblance of luck to find the "Ravenol" range of products. They produce a fluid for Haldex transmissions identified as AWD-H (P/no for 1Litre container 1211140-001) which is recommended for all the vehicles I have identified.
Link https://www.ravenol.de/en/product-range/special-hydraulic-fluids-1/ravenol-awd-h-fluid/
Note that the recommendation is to exchange this fluid every 60,000Kms.
More obtuse is that Ravenols Tasmanian Agent had this product on the shelf whilst the Tasmanian Volvo Franchises did not.
Price for fluid in Tasmania is $A55 for 1 Litre.
The Youtube Video, https://www.youtube.com/watch?v=uZNC06Z7imQ is a valuable resource and I have had no trouble dismantling the Haldex Unit using the procedure in preparation for parts and fluid to be delivered.