2007 XC70 125k. Transmission slips at lower speeds. I baby the car to avoid slip, but it happens occasionally.

Trans slips if we power around sharp turns, if I coast it no slip. Very occasional slip driving about 25-30. Not a daily thing and I am careful.

How best to diagnose issues? Are there certain likely issues from these lower speed symptoms?

Considering buying a 2006 s40 parts car with locked up 2.5T motor & good transmission. I can get the Transmission numbers - is there a reference on what transmission numbers will work for my 2007 XC70?