2006 Mazda 6 - Won't shift passed 3rd gear. Please help.?

My '06 Mazda 6 is having transmission issues and I have only basic knowledge of cars and no one in my area is familiar with Mazdas so i came here to find help. As you can tell by the title, my main issue is that it will not shift passed 3rd gear. It hard shifts into R when i first start the vehicle. It shifts... show more My '06 Mazda 6 is having transmission issues and I have only basic knowledge of cars and no one in my area is familiar with Mazdas so i came here to find help.

As you can tell by the title, my main issue is that it will not shift passed 3rd gear.
It hard shifts into R when i first start the vehicle.
It shifts rough from 1 > 2 > 3, but then doesnt shift passed 3. If I come to a stop it will down shift back to 1 and the cycle restarts.

The AT codes that it shows are: P0715 & P0766.

I hope this is enough information to at least get some ideas of what I might try to fix it.
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