2002 explorer hard turn clunking noise

2002 explorer AWD loud clunk when the wheel is turned hard left or hard right. Sometimes it's so violent it almost stops the truck. Local mechanic points to the transfer case. Front end checked out OK. Steering checked out OK. 4 wheel alignment was done. Tires rotated. any other ideas before spending $2000.00 for transfer case? Also, and I don't know if this is related or not, I get a vibration felt through the whole truck which seems to be coming from the front end at speeds of 65+. Mechanic also feels the vibration could be caused by transfer case.?
any and all help would be appreciated.

Transfer case seems like a logical suspect. However, you'll also want to inspect the front CV joints and front differential. If the front CV joint boots are not split and leaking, it's unlikely they are a problem, and you mechanic probably would have noticed if they were and he actually examined the vehicle.

If the CV joint boots are good and there is nothing obvious with the halfshafts, I'd suggest you have the fluid drained from the front differential and front the transfer case. Inspect the fluid for signs of metal or being "burnt."

-Rod

Just a heads up for 2002+ owners. The above problem appears to be related to the 4x4 module......Shift motor has been unplugged from transfer case and so far no more issues. This is the plug from the 4x4 module. stay tuned.....................................

1 week with 4X4 module unplugged and truck is running fine. At this point I'm convinced it's the 4X4 module or associated wiring. Hope this helps someone!

Running fine now..but will it go in the snow?

No, it won't go in the snow. The point of unplugging the 4X4 module was for troubleshooting purposes only. Now I can focus on the module or cable for repair instead of a $2100 transfer case.

It is ok to unplug this? No ill effects to the drivetrain when driicing... highway driving?

I have posted a vibration problem... want to try this as a test. Where is the plug located so I can perform the "4X4 module test"

Thanks