four wheel drive clunking noise

[Pikemaster101]

i have an 01 silverado and lately when i put it into four wheel drive auto it makes a very loud clunking noise when it shifts in and out. What part could be causeing this and about how much is the part?

[Macgyver55]

Hopefully its as simple as a 20 dollar u-joint!

Kind of hard to say without hearing it, but what kind of miles are on the truck?

[Pikemaster101]

180000 miles aprox. where is this part located?

[efgh]

At either end of the front drive shaft or rear drive shaft.

[hawkeye43]

Does it clunking when you push the button to shift into 4 wheel drive. If thats it mine has done it since new its in the trasfure case, 228000 miles ago