gearbox problem

[Paullap]

HI I am looking for some help please , I have a 1998 3.4 c2 Tiptronic, I have had the engine and box out to do some work, all back together now, but I get a clunk/ jerk when selecting Reverse, If i go from P to R backwards and forwards it is not bad, but from R to drive it is really bad like taking up backlash, I have the following codes

P0778 Pressure Regulator 2
P0710 ATF Temp sensor
53H83 undocumented code
P0748 Pressure regulator 1

I am going to change the oil and filter to see if that helps.

Any suggestions would be very much appreciated

Paul