1994 f150 4x4 front end question
 

Evening; We have a f150 4x4 1994 extended cab 5.8 automatic with 193k on it.
We have tried to fix everything on the vehicle but we have came to a stump. The front end pops or bangs when you stop sometimes and take off usually with the wheels in a turning motion but not always. There is really no exact repeating the noise it is sort of random.
I have checked everything under the front end i can think of to find the noise , all the linkage and box and all moving parts.
after all that i decided the pros would be my best choice so i took it to a highly recommended front end shop to get the thing fixed. They checked the front end over and finally all three of the mechanics were checking it over and making it pop randomly.
Here is where i need help or suggestions since there are so many experienced ford guys here. They came to the conclusion WE HAVE NO IDEA what is causing the noise.
Any ideas of items to check that are not common and may be overlooked? Help appreciated.
Thanks

Is there any change when you engage the front axle?

Hanky I have not tried to either engage hubs or actually put in 4 wheel drive. I will get that done tomorrow. Thank you

I put the hubs in and the tc in both low and hi range and maybe its my imagination but it seems less popping? not positive.
Did put my hand on the hub on the drivers side and seems like i can feel a slack kind of pop in the axle going forward to reverse to forward. I am pretty sure i already put u joints in the front axles . I dont think the play in the front axle is causing the loud banging i am hearing ??
How do you physically check the radius bushings? is it possible you cant see the movement there and yet they pop?? Its hard to put your hand on them and feel without geting ran over to see what is happening there?
Thanks
One other question is it possible to pull the hubs and go to the full time configuration and maybe tighten things up there?

I went an checked the wheel backlash up on stands on the front wheels in 4 low hubs locked seems quite a bit but drivers not as bad as passengers side.
Then we took it on some rough country to try 4x4 to see if i was right on popping and after getting going we found it is much worse with it in 4x4 and seems tough to get it disengaged after driving a bit.
I did notice that sever bumps do not seem to make it pop only something to do with the power train , driveline. if that helps.
Im pretty sure the hubs system is worn out on both sides and maybe some of the front diff. If this make any sense? Im pretty sure this thing was run HARD and put away WET so i may be fighting a losing battle. I dont have any desires to change out the complete axles and diffs on this thing.
Any cheaper suggestions. Thanks for the help