1998 Chevy Astro front axle noise and vibration

My 98 astro awd has an intermittent shudder like driving over rumble strips at a turnpike exit alert and a whine or growl like mud grips on pavement(pass. Side). When van shudders, I tap on brake lightly and shudder stops. I already paid to have the c-v joint, hub, bearing where drive shaft goes into front pumpkin replaced.I found axle rod had slipped out of placein pumpkin and into c-v and damaged splines. He dressed splines and reversed shaft. Paid "mechanic" over 1000.00 for several wrong guesses at the problem.I can't send a donation right now, I will definitely be able to do so as soon as I fix the van and my money isn't the retirement fund for "mr wrong wrench". Can you please give me a clue as to where to start, My son has mechanic training but no drive train exp. He will be doing the work. PLEASE HELP!