I have a 2002 V70 and I have experienced a similar experience with my transmission.
the first time it happenend is when the car was brand new, 2 days old, and I was driving 30-35 MPH and was coasting down to stop for a traffic light, before I could come to a complete stop, the light turned green and I depressed the accelerator and the engine rpm increased but the vehicle did not gain speed. it was as though the transmission had slipped into neutral. I thought that possibly the traction control had kicked in, (the road was wet)and I kind of shrugged it off. the second occurence was when I was making a 90 degree right hand turn onto the freeway ramp ,and It was during heavy acceleration, that the engine rpms went way high and then the transmission jerked into gear. again, it seemed like the transmission went into neutral and then went back into drive and the front tires screeched ! again I attributed this to the traction control kicking in due to the presence of loose gravel on the road surface. so, I'm not sure what to think now. please give me more detail to as what the circumstances were when your tranmission exhibited these same behaviors. you have piqued my interest.
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You will never leave where you are until you decide where you would rather be - 2002 V70 stk, /w /tinted windows