I have a 1994 burban and it makes a very loud clunking grinding noise when im in 2 but when in 4hi and lo it dosent make a sound

 

Is it when you switch to 4wd?

 

Strange, I would have expected it to be just the opposite.

It's possible that your transfer back into 2WD is not complete (this is a separate function than Hi/Lo function).
I'd change the Fluid in your Transfer Case out, then thoroughly exercise the functions...several times.
Those being changing from 2WD to 4WD-Hi to 4WD-Lo and back, in that sequence.

Most times problems like this are because of little use of the 4WD.
Shellac builds up, and when you attempt to transfer, things stick and don't complete the transfers.

Use Auto Trak II, takes about 2 Quarts.