Ford Explorer 1996 4.0L 4WD BW4405 Vibration Problem

I have Ford Explorer 1996 4.0L 4WD.Question:  Trying to resolve a drive train vibration issue. Only occurs when front drive shaft is installed, and starts at about 50 mph. Bad vibration you can feel through the floor - can't really go faster than 60 or vibration is too much. Pull the front drive shaft and it goes away. Have tried two replacement front driveshafts, one reman, the other new. There is no play that I can feel at either the transfer case output or the front end input. Trying to figure out if I have a front end, transfer case, driveshaft or cv shaft issue. Both cv shafts have been replaced. Driver's is less than one year old. Passenger about five years old. Older truck that I need to keep driving for a while yet and really want to get this figured out. And don't want to throw buckets of money at it but would like to get 4WD operational again. Driving with shaft out now. Any thoughts?Answer:  You have the BW4405 transfer case. First thing we would suggest you check would be the tire diameter. It is very important that the tires all match in diameter.The transfer case has a variable clutch pack in it and if the system is showing slippage (different tire diameter) it will be trying to engage and disengage the 4wd system and cause this issue.Also this transfer case is known for rear case wear in the rear output bearing area. With the rear drive shaft off pull straight in and out on the rear yoke, you will notice play in and out and there shouldn’t be any. If this play is excessive you will want to address this also.You  can visit our shop at 11071 93rd Avenue N Suite A Maple Grove, MN 55369 and we can help you diagnose the problem.  See the other parts we can provide on our web site