Trailer Brakes Shudder when Connected to 2004 Chevy Express Van But Not with Other Vehicles  

I have a 2004 Chevy 3500 Express Van RV conversion with old 2006?Tekonsha controller , a 2001 Yukon with Draw-Tite, a 2005 Yukon XL 2500 with ??, and a 2011 Sierra with in-dash GM supplied controller. One of my tandem axle enclosed car trailers developed a PROMINENT brake shudder at moderate to high brake power settings when driving from the Florida Keys to Maryland towed by the one ton Express Van.. This brake shudder only occurs when towing with the Express van with the old Tekonsha controller. This Tekonsha looks like a Voyager with two side mounted wheels. The right wheel sets brake power,the left probably level. To be clear braking is great, no shudder, with the other three tow vehicles and their controllers. With each vehicle the trailer is rigged very level, so this is not the problem Oddly when towing with the Express Van, if I release the brake pedal and squeeze the slide on the Tekonsha controller, the red power indicator light becomes darker red BUT the shudder goes instantly away??? Trailer had all new backing plate/shoe/magnet kits installed shortly before I left the Keys may be 2,000 miles ago and new trailer wiring installed from plug to brakes. I had them rechecked by an independent trailer shop when I got up to Maryland which found brakes to look good. That shop towed the trailer and found no shudder, but they cleaned to shoes and drums in case a little grease had gotten by the seals after the previous brake work, and they readjusted the brakes. I suspect something in the old Tekonsha controller or Express van wires between trailer and controller. to be the culprit. What seems like it is the cause of the problem? What should I have done or checked next. Which new controller do you suggest if a new controller is recommended?

asked by: Bob J