How to flush the hubs(First, I never said any of this, and take no responsibility for any accidents that happen when this is done...):

1. Jack up one wheel. Use a Jack Stand. Block the other three wheels.

2. Remove the wheel/tire.

3. Drain the hub.

4. Fill the hub with oil. I use hydralic oil, it doesn't cost much.

5. Start the engine.

6. With the t-case in H (NOT HL or LL), shift into drive.

7. Quickly release the brake. (slowly releasing the brakes allows the differential to do a BTM which tends to move the Hummer).

8. The hub that is in the air will spin.

9. Let the hub spin for about two or three minutes.

10. Drain the oil, if not clean, repeat steps 4 to 10 until clean.

11. Refill with good quality gear oil.

I found, over the years, that it takes three or four flushes to do this.

This can be dangerous! You must be very careful not to launch the Hummer off the Jack Stand. Once you have done this one or two times, you will get used to doing it. It is not difficult to do.

BTW, while doing this (and changing my halfshafts) I realized that greasing the drive line was much easier if you jacked up one wheel and with a large screwdriver turned the drive line (I turn a brake rotor) to line the grease fittings to the correct location.

BTWx2, I painted the drive shafts yellow at each grease point! That way while turning things I know exactly where the zerk fitting is!

These two tips cut chassis greasing time greatly: those pesky drive shafts were always a PITA to grease due to the fact that the zerk fittings need to be aligned just right to get the grease gun on.