Truck bucking when hitting the brakes?

If by bucking you mean jerking, your gain is set too high.

Boost is too high.

My previous truck had an after market brake controller. It drove me nuts. Too much gain and the trailer would lock up, causing bucking and neck jerking that was comparable to being in a head on collision.

Higher gain was necessary on highway speeds though.

Lower gain at highway speeds, and it seemed there was no braking from the trailer at all. But, at slower speeds and city driving, the lower gain kept whiplash from occurring.

I was constantly fighting the gain and sensitivity settings on that controller the entire time we had that truck.

I was amazed when we got our current truck that had the integrated brake controller. The truck and trailer work in harmony together at any speed now. I keep the gain pretty high because I really want the trailer to be a bit more aggressive than the truck. But still that integrated brake controller makes both feel like a single unit. I'll never go back to an after market controller again.

My initial thoughts are, it's your brake controller. Turn the gain down and see if the whiplash goes away. If it does, then you just have to work with it at different speeds to find the sweet spot. And you may never find it, and have to continuously fiddle with it, between highway driving and city driving.

Try the gain first before anything else. Then, if that does not smooth it out, there's something else going on.

freewayrandy wrote:
My truck bucks bad when hitting the brakes. Too much gain or not enough?

In addition to that question, I think you should check your hitch closely for excess play or something coming loose. If it is a 5er, there might be a "shock absorber" in the hitch too.

Putting this question in "towing" is a bit confusing.

Without more information lets start out with,
Not enough truck,
Too heavy for your truck,
Bad or worn hitch,
Bad brakes,
Mis-adjusted brakes,
Cheap brake controller.
And thats just for starters.