bsacamano

Hey all,

I recently got a new 7x14 trailer which came with a 2 5/16 coupler-the type that does not have an adjustment nut on it. I have the correct size ball and the coupler is attached securely.

So question is: when I come to a stop with the trailer and that stop is more aggressive than a coasting stop I feel a thump as I come to a dead stop. Then when I accelerate out of that stop I feel another thump. My guess is that it's the coupler and trailer load moving forward and back on the ball but given the coupler cannot be adjusted....maybe it's something else? Or is there something I can do?

I noticed it on the way home from getting it so no unsecured load causing it-empty weight of the trailer is 2120. Question being for the towing crowd: Is this normal towing characteristics of something that heavy? Perhaps it's just because the trailer was empty? Will the thump add a lot of undue torque to the hitch/frame connection and/or driveline?

2017 2.7EB 2.55axle w. ITBC/aux cooler.

Storeman

It is the free play where the pin holds the hitch to the reciver. Some have more then others
Other than annoying it is not hurting anything . You my tray a different hitch and or pin and it could help or they do make some hitches that absorb this shock load.

PerryB

Its slip-yoke thump. Commonly referred to as "slip-bump". Look it up, its a VERY common issue. It doesn't hurt a thing but is highly annoying. Over the years I've had 2 trucks and an SUV do this. It isn't brand specific either, it's a function of the driveshaft design. The increased load imposed on the truck, by the trailer, is causing increased axle wrap during acceleration and braking which increases slip yoke travel. Eventually it'll start doing this without the trailer. You can pull the driveshaft and grease the splines in the yoke, but this is usually a temporary fix. It's not a sloppy hitch pin.

EDIT ** I guess theoretically it COULD be a sloppy hitch pin, but it would have to have a significant amount of play to feel it in the cab. I'd put money on the slip yoke.

old_programmer

I wouldn't expect slip yoke bump on a brand new 2017. In my experience it typically starts happening on older vehicles where the seal and lubricant has started to dry out.

Storeman gave one reason you can hear/feel a bump when starting and stopping. The other as you have said is the hitch ball moving around. I used to get a bump when taking off from a stop with my old tow vehicle. It was from the hitch moving in the receiver. I've noticed the hole on the F-150 is a bit smaller and I no longer feel a bump.

SixShooter14

Generally, I would agree. But there have been several reports of New '15 and '16 F150s with the thump when not towing. typically greasing the SY solves it for a couple weeks.

humblerb

I won't speculate on the cause of the OP's thump.
But, I will say, on my 2012, I first had slip yolk issues when my truck was probably about a year old. Maybe less than a year.

Pugga

iTrader: (1)

Does the trailer have surge brakes? The symptoms you're describing sound like what you get when you have a trailer with a hydraulic tongue.

bsacamano

It does not have surge brakes. I have changed the drop hitch and leveled the trailer out a little more, I think it is some kind of play in the coupler or hitch. I've put some more miles on it and the thump certainly seems to be coming from the rear of vehicle-I do feel that slight thump without the trailer of that drive line yoke and this definitely feels like it's coming from a different place. I am throwing a WD hitch on it and see if that changes the characteristics at all.

PerryB

Its considerably more noticeable with the trailer because the increased load causes more axle wrap upon acceleration and braking. It's the slip yoke.

Storeman

I don't see how a empty trailer this light weight could cause axle wrap.
I will stick with my original diagnosis.