Hi,
I've read a few posts regarding clunks in the front end of Blazers and thought this info might be useful. It's from the July 2003 issue of GM Tech Link: http://service.gm.com/gmtechlink/images/issues/jul03/TLjul03e.html

Clunk Noise Felt Through Floor Pan Affected Models:

1998-2003 Chevrolet S-10, Blazer

1998-2001 GMC Envoy, Sonoma, Jimmy (US), and Oldsmobile Bravada

1998-2003 GMC Jimmy (Canada)

Some owners of the listed vehicles may experience a clunk noise that can be felt through the floor pan

This condition may be caused by the torsion bar crossmember contacting the frame rails during left or right turns or on uneven surfaces.

Determine if the clearance between the left frame rail to crossmember and right frame rail to crossmember are equal. If not, install either a washer or alignment shim between the upper mount and frame.

Refer to SI document 539243. This document includes a component diagram of the torsion bar crossmember to frame rail assembly and may provide assistance in the repair.

- Thanks to GM Technical Assistance


Hopefully this may solve someone's problem. My dealer couldn't diagnose the problem until I gave them this.

Paul.

That or it is the hood washers that cause the same problem.