Last week I got my tranny changed on my Volvo s80 1999 2.9. Which works perfect except some times it does give a jerk from shifting 2 to 3rd gear. But its very rare.

lot of guys are recommending the update, so my question is

What is transmission software update, why we need it and where to get done beside Volvo dealer?

My 2nd Q.
My mechanic says he put 2003 s80 transmission into my Volvo s80 1999, and what ever he saying either truth or lie, I am not able to digest this......Is Volvo transmissions are compatible with their other models????