my stock 2002 blazer starts and engine runs fine but while fluids in transmission are fine; when warm it occasionally disconnects from the engine, and will not shift up or drive properly. code showed MAF sensor, replaced. Now problem is worse,

Possible causes I think - Connections bad , Engine Computer, Transmission

Where do I start?

 

Start with scanning the ECM. No shift probably means shift solenoids. It has two and they are not difficult to replace.