[tomp]

The diffs are open on front and rear. There is no limited slip feature.

The rear locker is a very good addition to any off road vehicle.

Due to the weak design of the H3 front housing, I would not put in a locker until GM beefs it up. After that, replace the front assembly if it ever breaks to the later model and add the locker. You will always risk breakage if you are not careful regardless.

Yes, the eaton is OEM from Hummer. The one trail duty offers is a real nice unit and Phil over there is awesome.

Adding a true locker does require replacing the entire diff assembly, just as the one from Trail Duty is a complete locker/diff.

Adding a locker is the only way to get both wheels spinning together. IMHO a 4X4 without lockers is not really a true 4x4 as you can not spin all 4 wheels together. However, there are ways around this, such as BTM. Taking the time to learn what this is and how to effectively manipulate the capabilities of your Hummer, is what wheeling is all about.