Auto body repair & detailing: prep required for repainting 93 Chevy Suburban, razor blade knife, chevy suburban

Question
I have a 93 Chevy Suburban with the famous GM white peeling paint. All the horizontal surfaces are about 25% gone and the upper portions or the vertical portions show either minor flaking or something that looks like "crazing".  I am in the process or prepping it for repaint and I would like to know how much of the old paint has to be removed.  Do I only need to remove the loose paint or do I need to strip all the horizontal surfaces to the factory primer.  My concern is if I repaint over crazed/degraded paint my new finish coat could fail if the original paint degrades further and either flakes off or cracks under the new finish.  

Answer
Your concerns are well founded. The crazed paint needs 100% removed, the peeling panels need the paint removed and as much of the factory primer saved as possible. I always peeled back the paint with a razor blade knife, it saves time, and where it stops peeling you can start feathering the paint. Take duct tape to the vertical surfaces, lay out long strips of it, and just rip it off of there. If it passes the tape test, it doesn't need stripped. However, even if it passes the test, if there are fingernail sized flecks of paint missing from a panel, it's just about to start peeling- this will need stripped. With the age of your truck, I figure you may well wind up stripping the entire truck back to the factory primer. Bill