4x4 clunking problem

[zgarbuz]

I recently bought a 93 Ford Ranger with a 4.0 engine, auto transmission, electric tranfer case and auto locking hubs.
Everything is fine when I'm in RWD.
When I switch to 4x4, and start driving slowly, (1-5mph) I have this clunking noise coming like from approx. below the gas pedal. Every so often, I get this loud thump that I hear and feel directly under my feet. Due to this noise, I never drove faster then 5mph on 4x4.
I need the 4x4 for this winter, but don't know where to start to get this fixed.

Thanks for all the help

 

[KELLY88]

Do you have the automatic hubs? One of them could be failing to engage all the way causing them to pop in and out giving you that noise.

 

[zgarbuz]

Thanks.
Since I'm new to fixing cars, how do I check the hubs to find out if they are bad?

 

[Ranger#1]

i have the same probb how do i fix that