I have a new to me 2006 XC70 in great shape with 250,000 km or 150,000 miles. The transmission is not perfectly smooth on shifting. I've heard it both ways the changing the fluid blows the transmission and others say its works great. The volvo tech said even volvo suggests you leave it... Whats the ...

So please help me understand what is going with changing the fluids and the downsides of flushing etc .