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 ...

If it goes bad when you replace the fluid it was already bad but just hadn't shown it quite yet.

If you really want to play it safe then add an inline filter to the return line then replace what drains from the pan a couple of times with some driving in between.

I'd say you can save this tranny by starting to do a few "drain and fills". That "never touch it" philosophy is bogus.

Dirk

Do an incremental 'flush and full' as described in this video: https://www.youtube.com/watch?v=leBtEnEDAtc My car was showing typical symptoms of 'shift flare' where the 2nd ->3rd shift seemed like it would briefly go into neutral. I don't think the transmission had ever been serviced (111,000 miles...

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

When I got my 2007 XC70 with 121k miles last May I immediately did an ATF sump drain and added in 3.65 quarts of Mobil 3309. During the next oil change 3 months later I did another ATF sump drain followed with a return line drain. With the return line disconnected from RAD I'd start her up and shift...

Just chinning in but the idea is clear: as everybody above, a few drains (that should be about 3.5L each) done a few months distance is the safest way. Using any 3309 oil (Toyota, Mobil 3309) I did read of two situations when a full flush all at once on a high miles transmission that was driven most...