Surging in the transmition.

My 92 Full Size blazer, 350v8 700r4 4x4 is surging when i push the breaks it stops. I read in a magazine today that someone was having
the same problem and fixed it by adjusting the brakelight sensor ( i believe ) has anyone had the same problem and solution. If that could be the problem how do i adjust or replace the blake light sensor. thank you for your help ahead of time.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.