Happy holidays -- hope the board can help me with this one:
99 Blazer 4 wd. When I transfer from 4 to 2 WD while moving there is a big thud as the front wheel drive disengages. Does not happen when going from 2 to 4 wd, only from 4 wd to 2 wd. It feels like it is coming from the right front. Thoughts on causes, cures and costs??

 

My RAM used to do the same thing. I think it's just the front axle disconnecting at the actuator on the passenger side of the internal axle shaft. It could mean that the actuator isn't working fast enough causing a delay between when the 4wd is disengaged and when the front axle disconnects. I think that the axle disconnects so that there is less drag while in 2wd...