what would cause all my gears to go out on my 2005 H2 Hummer when i am driving down the road and now i can not get the tranfer case to shift into 4 high or 4 low and neutral can anyone tell me please

 

Not sure what would cause it to do that while driving down the road. It sounds like somehow the transfer case got itself into the neutral position but it could be some other issue with the torque converter or the transmission I guess.

One thing I did discover on mine. When I got it, it would not shift into 4LO Lock or Neutral. It would shift into 4HI Lock and of course was fine using in regular 4HI. On checking things I found that the transmission fluid was about 1.5 quarts low. After I added the transmission fluid to the proper level the other day it will not shift into 4LO Lock and Neutral. Not sure if any of this will help though.

If its the transfer case and it has somehow shifted itself into neutral then the transmission will not hold the vehicle even in park and will not work in any gear. If it still holds in park then its probably not the transfer case.

On these (al least on my 2003), according to the manual, the only time the transfer case should be in neutral is for having the vehicle towed.
"Shifting the Transfer Case Out of NEUTRAL
To shift the transfer case out of NEUTRAL, do the following:
1. Set the parking brake and apply the regular brake pedal.
2. Shift the transmission to NEUTRAL (N) and turn the ignition to RUN with the engine off.
3. Press the button for the desired transfer case shift position (4HI, 4HI Lock or 4LO Lock).
4. After the transfer case has shifted out of NEUTRAL the indicator light will go out.
5. You may start the engine and shift the transmission to the desired position."