I'm having a new issue with my trailer brakes. This will be the third season with this truck and trailer combination, but the problem has just started this year.
The trailer is a 6500-pound travel trailer. When I apply the truck brake, the trailer brakes suddenly and abruptly grab (jolting the entire rig) and release, then do it again sometimes as
many as four times before I come to a stop. I apply the brakes consistently with no sudden changes on my part. The grabbing does not generally happen below about 20 MPH
The dealer could not find an issue with the truck, but they did not have the trailer when they tested it. Funny thing when I did take the trailer to the dealer, it did not happen when I was driving there so they did not even look at it that day. Although, it started doing it again on my next trip 3 days later. I towed my trailer with a friend's 2021 250 SD without a problem. I have
adjusted the gain higher and lower which does not really change things much. I have sprayed contact cleaner on the plug and receptacle - no change. It could be
the trailer but since it did not happen when it was towed by another truck, my thinking leans to my truck as the culprit. I have seen some recall notices about brakes/controllers; my
vin is not in any of them. Any thoughts on where to look or proceed to find a fix?

Thanks in advance !

My rig:
2022 250 SD 30,000 miles
Built in Brake controller
6500-pound travel trailer
15,000+ miles on truck and trailer together

 

SOME trailers are more finicky than others when it comes to their brakes. So I would still be inclined to look at the trailer. However...

What settings do you use on your truck for your brakes? For a 6500 lb travel trailer (and really ANY RV) you should be using 'light electric' if it's an option. It should be, as it was on my FIL's '22.

Where do you have your gain set? For our travel trailer of roughly similar weight, I set it at about 4.5-5, maybe 5.5 and have never needed higher. Our flatbed I set at 4-4.5 if there's something on it, I've dropped it as low as 3 when empty to keep the tires from locking up.

 

I've had the same experience. Trailer brakes are extremely "grabby" when I hook up and stay that way for the first 5 or 10 miles down the road, then it gets much better. I think what's going on is that the drum brakes that trailers use have a tendency to get surface rust and scale built up on them very quickly. So when you first hook up to the trailer the shoes on the brakes will grab the drums and jerk the trailer around. After some friction cycles the surface on the shoes/drum goes back to normal and the brakes become smooth again. In short, it's completely normal.

 

Many RV dealers have equipment that will plug into the trucks 7way RV connector, and can measure the output to the connector. Many of these devices have a wire harness that reach into the cab allowing dymanic testing. I had a similar experience on my last super duty and the culprit ended up being an intermittant short in the trailer plug / wire harness

 

I ran a "feedback" loop for just this purpose. Only mine it is permanent.
I already had a separate connector to trailer, for my aftermarket trailer cam setup,
So just used one more wire, tied directly to the electrical signal brakes are seeing.

I mounted small digital voltmeter in dash, but there is no reason you cannot run
a temp wire, directly from brake wire on trailer, back to cab and use a std voltmeter.
Could even use it on buddies truck, see if your voltage is spiking compared to theirs.

 

i think I would pull a trailer brake off on each side, just one and have a look.

 

I have not yet opened any of the trailer hubs yet but that would be next. I may have blown a grease seal or possibly have a worn Brake magnet.

The gain setting I use is anywhere from 4.0 (too light) to 6.0 (too heavy). But usually run about 4.5 - 5.0 . Heading down the road, I varied the gain to see if different settings help, they didn't.


The controller has a "Brake Effort" setting of Low, Medium or High. I run with Low.

The other setting is for Hydraulic or Electric. I use Electric.

My controller does have different trailers. I set one up for this trailer and I do ensure I'm on the correct one. Actually, I deleted all of the others I had to be sure the wrong trailer was not selected.

The Grabbing happens well after any crud is rubbed off of the drums. It can begin immediately and lasts for hours/miles.

I believe the dealer put a test fixture on the truck to test voltages. But they did not test it while I was driving.

I have a couple months before we head out again. Sounds like I'll be looking inside the hubs.

Thanks for the input!

 

annual brake inspections and re-packing and new seals depending upon use is also a good idea.

 

Troubleshooting takes common sense. Try the manual control to apply the brakes. If it still acts the same it's more than likely the brakes. Manual should apply full voltage and keep it until you let off. If manual works but automatic doesn't then somethings wrong with your TBC

 

When I have had "grabby" brakes, they've typically been gummed up/contaminated. I agree with those that say it's time to pull the drums and have a look. Let us know what you find.

Dave

 

Thanks for the suggestion about using manual mode I'll certainly give that a whirl first. It'll be a while before I can get to it as I'm
busy for the next two weeks. I took the trailer back to the place where I store it this morning. In route, I did notice that the gain on the dashboard display under Trailer Information
changed and flashed while I was stopping. It went from 3 bars to 0 bars then back to 3 or 4. The flashing somewhat coincided with the grabbing. It was a bit difficult to watch the display
and drive at the same time. I did try to take a video of the display while I was stopping but that did not feel like a smart thing to do. (I'm older now,
I can only do a few things at one time).

When I get back, I'll get right on it and let you know what I find out !!
Thanks again

 

I don't think this is true. Manual applies the trailer brakes to the set gain level. One technique for setting the gain is to drive about 25 mph on a straight, level road and apply the trailer brakes using the manual trailer brake control (do not touch the truck brakes). The gain is set to a level just below the level that makes the trailer brakes lock up.

Manual braking has a purpose. It would be dangerous for manual to apply full braking power if the gain was set to a lower value.

 

Isn't manual variable, up to the set gain level? (if pushed all the way over)

 

The farther you push it the more voltage is applied. I can go down the road and press it hard and my brakes lock up

 

Try reducing the gain and see if they still lock up when pressed hard. As I wrote previously, I set the gain for various trailer weights by pressing the manual lever fully. The voltage level may vary the furhter the lever is pushed but I think the maximum is limited to the gain setting at the time.