Im from sweden so my english arent so good, but i will try to explain what problem i have.

When im driving and its shifting up to 4th it quickly jumps back to 3th. And sometimes it shifts good. A dealer has searched the gearbox for problems but couldnt find anything.

Ive changed the oil and filter severeal times.

I only get the code p0734.

 

There should be a thread on here, on testing and replacing shift solenoids. I would say maybe output speed sensor. Usually that shows up in first gear.