Hi ferret, Tom is right on trucks with manual hubs you can use low range to the rear with the front hubs free. Without manual hubs there is usually a way to defeat/overide the engagement of the front axle. Not sure what you have but on my last truck(96 Tahoe) there was an actuator on the front dif. - electric solenoid that turned like a screw to mesh the gears. If yours has something like this - look for a fuse or crawl under and pull the plug.
The only thing you have to concider is that in 4L you are transfering a lot more torque to one drive shaft then it was designed to handle. Be very gentle on the gas and check your U joints. Not trying to scare you but if you did blow a U joint backing up the hill - you would be stuck with your foot on the brake until you could coast to a level spot. You would be immobile and putting it in park would do nothing as both your front and rear wheels will now be freewheeling. :shock:
Sorry but I had to add that disclaimer :!:
You might be OK in 2H - but pushing/pulling a heavy trailer up a steep hill in too high a gear puts strain on the clutch or A/T.
Lots of Bratts here cheering for you - if we all got together we could carry your boat in your driveway!
Good luck, Rob
