Can sync 2 be installed in a 2017? Or only sync 3? I have the 4" screen but came across a sync 2 screen and apim today for $25

 

Either can be installed. I'm not sure $25 is a good deal. Sync 2 AKA MFT is exceptionally terrible. You would need to buy the bezels and other parts anyway, so if you're going to spend that kind of money I'd go for Sync 3 an aftermarket deck or just leave it alone.

 

What is so "exceptionally terrible" about Sync 2? It's what is in my truck and I have yet to have a single issue with it. Just curious.

 

The GUI is slow on good days. It does not support Android Auto or Apple CarPlay. It does not support new OE navigation content. It does not support mobile apps. It is not capacitive touch compatible. It's known to frequently drop bluetooth and/or brick itself. It is a decade old and no longer supported. It's notoriously unreliable to the point that Ford abandoned their relationship with Microsoft directly as a result.