I did my 97 960 at 67K miles and it made a huge difference in the shift quality.
I did a pan drop and a complete fluid exchange using Redline D4ATF.
When that drain plug was opened, what came out was nasty brown and smelled really bad.
The shifts were a little slow to engage before my transmission flush.
I had a little bouncing in and out of OD for the first 1,500 miles after the flush. I figure it was just getting the bad stuff out of the nooks and crannies. Now it shifts smooth as silk as they say.
At 97K or about six thousand miles I'm doing a drain and refill.
At 30K after that I'll do another total fluid exchange.