At the girlfriends house and drove the blazer, as soon as I got off the highway yesterday I hear a noise that sounded like an airplane motor bogging down. I had it happen before, and if I hit 4x4 it would quit, then I could go back to 2hi again. now it does it when in 4x2 nomatter what, so I unhooked the line. Now I need to get home, and its drifted in places 12" deep,then not at all in others, and I'd like to beable to use it when I need it. Any idea what this could be? thanks

 

I do not know too much about Blazers, so this might not be any help. However, this sounds like a problem that Range Rovers have when the electric motor controlling the transfer case's lo and hi range settings goes out or starts to slowly slip out of place. When this happens, the vehicle makes all sorts of strange noises and exhibits odd behavior as well. In an emergency situation, we have been able to get under the vehicle and manual move the electric motor with a screw driver to the setting we want it at. Good luck and hope this helps.

 

check your cv's for throwing grease. if they are, they have been leaking for a long time and now the bearings are running dry and siezing up. i had this problem and it sounded like a street bike passing me, and when i loaded up the cv by hitting 4hi the sound would go away. another possible situation is the vac switch on the t-case is faulty and allowing a small amout of vacuum thru and slightly apply the front diff. a way the i use to see if the switch is leaking in 2wd is pull the battery and tray, unbolt the 4x4 actuator, undo the vac line and install a vac gauge, temp install the battery and start it up and look at the gauge. in 2wd should be 0inhg and in 4x4 the gauge should read between 15-20inhg. may be someone will chime in with a easier/different way. This is how i do it as a mechanic soo i can show the customer where the fault is. let us know what you find.

 

Its not a gear grinding sound, its almost reminds me of a water pump on a travel trailer.