Sudden jerks from trailer brakes

[T and C]

Sometimes this forum amazes me. During my last trip I encountered a new situation that had me worried and completely at a loss to explain. I had just towed my TM over the Donner pass and down to Sacramento on I-80. I turned onto an off ramp to switch to US-99. It was one of those ramps where you circle around 270 degrees to enter the slow lane of the new road.

Suddenly there was a sharp jerk from the rear of the truck or trailer. I immediately pulled over to check out the trailer. I had no idea what had caused it. I evaluated some possibilities:

1. I had run over something on the road. However, there was nothing on the road behind me and nothing dragging under the trailer.

2. I had hit a pot hole. But there weren't any. I had stopped in a wide place at the base of the off ramp and could see most of it.

3. I had dropped a wheel off the pavement. However, there was a wide, paved shoulder on the ramp so that could not be it.

4. I had a flat. But a check of the tires showed that the tires were ok.

Needless to say I was puzzled by this. A CHP officer pulled up behind me and we discussed all these possibilities and he agreed that there was nothing on the road, etc..

The one common factor was that the four times that this happened over a one week period of towing was that I was on a tight curve every time. Once on the off ramp, once driving up to the Yosimite area, and twice in the Kern River canyon going up to Lake Isabella from Bakersfield.

I went on line this morning to ask the other members for help in figuring this out. I decided to read the new posts first, and then I read this:

Originally Posted by PopBeavers
On my 3008 GMC 2500HD truck, when tow haul mode is engaged and the ABS brakes activate, the on-board computer in the truck pulses the electric power to the trailer brakes.

I call this virtual ABS.

Not all tow vehicles have this feature. My 2002 Chevy 1500HD does not.

My Ford F150 has a version of this. It is part of the anti sway feature. It will automatically apply brakes on one side or the other to bring trailer sway under control.
__________________
2006 TM 3023
2010 Ford F150 SuperCrew FX4

I'll bet that is it. I also have a 2010 F-150 with the sway control feature. When I go around sharp curves the truck computer thinks the trailer is swaying and activates a brake on one side. The "jerk" only lasts for a second or so, and once it did it twice in succession, real fast.

Do you think I'm right? Or not??

And thanks to PopBeavers and MHatcher.

Tom