toyota tacoma four wheel drive

2004 toyota tacoma six cylinder tdk, 12,ooo miles on this vehicle. ive got a problem with my four wheel drive, this only happens as i come to a stop, i depress the clutch to down shift and as i put my foot on the brake peddle it feels as if the gears are grinding terribly. but the grinding is felt in the brake peddle not the clutch. this has happens every time i come to a stop in four wheel drive. please help!
thanks
ray