The proportioning valve on a 1992 Chevy Blazer S10 4x4 is typically located
on the frame rail, near the rear axle, and close to the master cylinder lines. It's often hidden somewhat, so you may need to look closely and potentially use a flashlight. It's usually a small cylindrical device with lines running to and from it.
However, the exact location can vary slightly depending on the specific model and any aftermarket modifications. It's best to consult a repair manual specific to your year and model Blazer to be absolutely sure. A diagram in the manual will be very helpful.
