I got a 02 V70 xc AWD 2.4 light pressure turbo about 2 months ago. The used car dealear was afraid the trans was going out so I got a deal on it and even if I replaced the trans it would still be under blue book value. The AW55-50 trans was about 1 quart over filled and the fluid was like black ink. The car would shift fine when COLD but after the trans warmed up , about 15 min. it would slip in 2-3 and 5-6 up or 5-6 down shift it would rev to 5 or 6 grand and bang in hard also in a slow coast it would slip then slam when you press the gas lightly or hard throttle it dident matter.

So I drained 2 to 3 quarts and refilled with Valvoline Max Life multi vehicle ATF. it says it meets Volvo BMW Toyota on and on.......
I did this 3 times over to try to get all the fluid changed, the coast then bang got better but the 2-3 and 5-6 slip was the same. Then I put in a can of seafoam Trans. cleaner. No change...
I had a strong feeling nothing was broke because cold it was shifting great for 10 or 15 minutes!

Then I put in the new IPD updated servo cover to help the 5-6, NOPE no better, same slip and bang in 5-6
The ATF fluid was still dark so I looked around the net to find other fluid info, this asian warner 50-55 or 55-50? cant remember, It is used in a lot of other brand cars ,lots of Toyota to they own part of Asia Warner I read.
So I went with the toyota type IV or 4, same as the Mobil 3309 or a jws 3309 spec. I dont know of many jws 3309 spec fluids and the toyota dealear had it just down the road so I got a case of 12 quarts.

I got a spare green clip and disconnected the top trans cooler line"the old clip broke" I put a drain tube on the trans cooler and a funnel/hose on the line. I would start the car drain 3 quarts then add 3 of fresh type 4, it took 10 quarts till I got fresh type 4 coming out. I then put on the new green clip and pushed it back into the cooler, ran the car a minute then put in another half quart to bring up to the cold full mark.
I drive the car for 45 miles so far on 2 trips about 1 hour time and not one slip or shift flair , it seems to shift at a lower rpm now also. I think it is fixed !! I will tell anyone who asks ONLY use Toyota type 4 , oem Volvo, or Mobil 3309 ATF or you will have problems! I dont believe a lot of stuff on the net a lot of it is just opinions but I know from trying the valvoline multi ATF it just dont work. I cant say about any other brand ATF I havent used any, but this 5 speed trans is like a Swiss watch inside be careful !!!
I hope this can help someone out with a trans slip issue

 

I'm having the same "coasting" issues as you were; with a rebuilt trans (dealership rebuilt it before I purchased).

Thanks heaps for your tip with the fluid, I'm betting that the dealership (not a Volvo dealership) didn't use the correct fluid after the rebuild.