According to my bible
4 06 1
Steering
ball joint nuts.............................. 40 Nm or 30 lbf ft
For some reason they don't refere to them as TREs but they are the same thing. the value is aproximate as you will probably need to tighten them up/un do them a fraction so that the hole in the TRE lines up with the castalations on the nut, assuming the TREs you have use a split pin to stop them turning.