I've got a 2008 H2 SUT.

I can engage the rear locker, no problem. Getting it to unlock seems to be pretty random.

I've tried all these combinations and can't seem to get it to do the same thing twice.

in neutral, drive forward, drive reverse, rolling in neutral fwd & rev, shift to 4 hi, press the lock button (obviously!), drive a long way fwd & rev, tight turns, slight turns, drive > 40mph

When I press the button to unlock, the lamp goes off, but it's still locked. Shift to 4-hi, the lamp goes off but is still locked. Pretty annoying.

Any ideas?

 

It's a 2008 you probally still have warranty, bring it to the dealer and let them figure it out.

 

Shift to 4lo lock. Put in reverse and do donuts or figure 8's it should unlock. Then take it to the dealer for inspection.

 

I agree, but like HumminBoatin said, get it unlocked before you drive it to the dealer. If you drive it on highways locked, you're going to create even more trouble.