Be careful. On Ford 4R100 trannys, which are used in the SuperDuty trucks, prolonged backing up under heavy loads can overheat components and cause damage. Many tow vehicles failed in remote campsites while backing RVs up a hill.
It is possible that this is true with the ZF as well. Why else would torque limiting occur?
2009 Murano LE AWD - Traded
2003 Excursion 4x4 7.3 PSD - DIESEL
1985 Mercedes 300SD - DIESEL
JGC LIMITED 4x4, CRD, MAXSTEEL-BLK/FROST INT, LG2, ORA2, BLK HTR, NAV., CD - DIESEL!
Harley FLSTFI '04