I have a 98 XK8 with 141K miles. It has been pretty much a trouble free car. About a year ago it started shifting funny between 1st and 2nd gear, like it was binding up a little. Then the other day I stopped and it like went into neutral and moved very slowly (limp mode). I turned the car off and it started working Okay again. It did it again a week later but this time it stayed in limp mode. I pulled codes from the trany P0706, P1797, P0731 and P0790. I cleared them all and it didn't change anything. Now the only code I get is P1722. Since it started doing it all of a sudden, would I be looking at a computer problem or a hardware problem?

 

Search A - drum / pressure regulator before you do deeper damage . The defective pressure regulator is cheap ( 55 dollars ) and can be swapped DIY by just removing the pan .

May not be spot on but is very common on the ZF5HP24 Xmission

 

As Lady P suggested it might be the A drum. Dropping the pan and looking for metal fragments might confirm. I did have one A drum repair I did that it didn't deteriorate enough to leave fragments in the pan.
If the A drum has failed changing the pressure regulator without repairing the A drum will not fix the problem. It is a good idea to replace it at the same time you are doing the A drum repair.

 

I've moved your post from the X308 forum to the XK8/XKR (X100) forum.