got the same bike and had a few issues with this as well. the answer IMO is to slow to below 15 mph and flip the switch. the main thing your looking for is for all four wheels are moving at close to the same speed. i got stuck in a mud pit in 2wd and tried to switch it to 4wd. the clanking sound that proceeded from my front diff didnt inspire alot of confidence. my brother makes the mistake of flipping the switch while he's nailing the gas which is a good way to grenade the front diff.