Yuri,

Below find a summary of the official Volvo flush method. I've done it and it works.

CHANGING TRANNY FLUID 850/X70

Car on ramps, blocks, jackstands, etc.

Drain tranny fluid into pan. Plug is at bottom of tranny below axle and runs in same axial direction as axle.. Replace plug using new washer. 18 Ft lbs.

Remove battery and tray to get access to top of tranny.

(Air pump is mounted under battery tray.)

Remove hose on top of tranny by loosening nut. Hose is taper fit into tranny.

Plug tranny hole.

(Connect battery to car using jumper cables to avoid having to reinstall it)

Fit clear plastic hose to reach drain pan over end of tranny hose.

Add 2 qts of tranny fluid thru dipstick opening (I like the Mobil 1 Synthetic- used 11 qts total. Tranny actually holds 8 qts so you're not wastiing much.)

Tranny in P. Idle engine until bubbles appear in fluid.

Repeat fill and idle cycle until fluid runs clean.

Replace hose, battery tray and battery. While idling, wlith parking brake on, run shift thru each position for 4-5 seconds.

Careful not to overfill tranny after last cycle.

I now recommend the alternate method which skips draining the fluid thru the plug and battery removal. Instead disconnect the upper fluid hose at the radiator. Make sure you have a spare retention clip as they have been known to break. Also have a 5 ft length of 3/4 or 7/8? ID plastic hose and a hose clamp to put on the radiator fitting since that is where the fluid will exit. All else is the same. Good luck.