draining sub tank into main tank?

[the evil twin]

thanks guy's i thought you just switched between the 2 tanks like in the cruiser (bloody toyota drivers haha) thanks again

Nah mate, the Patrol's simply have a transfer pump that puts the fuel into the main.

Couple of things to know...
If there is fuel in teh sub the system does a short self test each time you start so the subby will eventually empty itself into the main without you initiating it.
If it fails this self test it will illuminate the Sub Tank warning light on the dash to tell you the fuel is "unavailable"
To actually transfer fuel from the sub the main needs to be well below 3/4 full on the gauge (this varies from vehicle to vehicle).
The light in the sub tank switch will stay illuminated while fuel is transfering but the sub tank computer will switch off the pump (and the light) above 3/4's in the main so it doesn't hurt to try the switch again after you use a bit more fuel to get the last out of the subby (unless the main was very low initially).
The transfer rate is around 1 to 1 1/2 LPM so it takes about 20 to 30 minutes or so to transfer a full standard subby to the main.