4H to 4L - With front hubs locked the lever may be moved whilst vehicle is in motion.
Clutch must be disengaged. To prevent the engine from over revving vehicle speed must
be within the following ranges below:-
Transmission gear lever position and speed MPH - KM/H:-
1st,10mph - 15km/h,2nd,15mph - 25km/h,3rd to 5th,25mph - 40km/h
I hope this helps,I found this in my Vauxhall Frontera Driver's Manual.
R.I.P Sable!(2005 to 2013)