99 Yukon downshifting

I have a 99 yukon that seam to have a problem with the trans not down shifting. If I come to a stop at a slow roll the trans seams to downshift with out any problem. If I come to a quick stop the trans will not downshift ontill I accelarat. you here a clunk before the truck stars to move. Like a down shift. Seams to shift ok going through the gears. Any one have any ideas.

Thanks

Welcome to AF, this clunk maybe the driveshaft yoke binding in the transfer case, common issue, GM makes a special lube to correct this, the shaft comes out and the ft yoke is lubed with this grease.