Pulsing During Braking

[UnklJoe]

Hi,


I'm out of ideas and need some suggestions/previous experience, please.

The details:
--2015 RAM 3500 Cummins TurboDiesel Automatic Transmission 4x4 with factory brake controller (26,000 total miles, not all of them towing)
--2015 Airstream FC27 (probably less than 10,000 total miles)

The last couple of times I towed my AS between my home and the storage yard (about 3.5 miles each way), I heard the street side wheels screech as if they were locked-up when braking (from about 25 MPH). So, this last time I brought it home to pack before this trip I used the Jack-Rite/Trailer Aid to lift the wheels one at a time and spin them then apply the brakes from the truck. All wheels stopped when the brakes were applied (I was thinking the curb side brakes weren't working).

During my trip to the campground about five hours into the trip (over mountain passes in Colorado) the rig (TV and AS) started pulsing when the brakes were applied lightly; applying them harder stopped the pulsing. I was using the same brake controller gain setting I used without any problems last year. I stopped a couple of times to check the brake drums and no drum was excessively hot to the touch, and all of them were warm (street- and curb side). I use my exhaust brake and lower gears on the down-sides of the mountain passes, so I'm not riding my brakes.

I tried increasing the brake controller gain setting, and decreasing it--with no success. The pulsing continued. I don't believe (but I don't know FOR SURE) the pulsing was caused by the truck's ABS due to little or no braking being applied by the trailer. The brake controller gain is usually set at 6.0; I went to 8.0 and 4.0, with no change in the pulsing. Again, the pulsing was most noticeable at low speed stops/deceleration, and went away if I pressed the truck brake pedal harder. So, my thought is that it's not the ABS; the pulsing also seemed a little faster than when they are pulsing when stopping on ice (don't know if the ABS makes adjustments for pavement conditions or not--I think it's just if it detects lock-up of the truck wheels, which was NOT happening in my case).

I usually carry about 75% fresh water, and about 20% in both the grey- and black water tanks when towing (for rear weight balance, and to slosh around in the grey and black water tanks to loosen any "deposits").



Once at the campground I have checked AS wheel lug nut tightness; none were loose, and all were within a few lb-ft of the required torque setting.


I checked brake fluid level in the truck; good.

I checked the hitch ball nut tightness; good.

I checked the receiver and pin for excessive wear; none.

I'm out of ideas here.

Suggestions? Previous experience? I don't think the braking was at all inhibited during the pulsing, or at any other time. It's like when disc brake rotors get warped and need turning--but my truck only has 26,000 miles on it, and not all that many towing miles. I set the brake controller gain by using the brake controller manual slide to stop the rig from about 10-15 MPH in a reasonable period of time without screeching (locking up) the trailer wheels. (That's how my grandfather taught me, and I don't believe that's changed in decades--but I may be wrong. I've been wrong before, and I'll be wrong in the future. Just ask The Wife. )

Thanks in advance for any advice or previous experience. I've looked through the Forums and didn't spot anything particularly related, but there are a LOT of posts and not everyone uses the same terms to describe the same phenomena....

[paiceman]

Originally Posted by UnklJoe

Hi,


I'm out of ideas and need some suggestions/previous experience, please.

The details:
--2015 RAM 3500 Cummins TurboDiesel Automatic Transmission 4x4 with factory brake controller (26,000 total miles, not all of them towing)
--2015 Airstream FC27 (probably less than 10,000 total miles)

The last couple of times I towed my AS between my home and the storage yard (about 3.5 miles each way), I heard the street side wheels screech as if they were locked-up when braking (from about 25 MPH). So, this last time I brought it home to pack before this trip I used the Jack-Rite/Trailer Aid to lift the wheels one at a time and spin them then apply the brakes from the truck. All wheels stopped when the brakes were applied (I was thinking the curb side brakes weren't working).

During my trip to the campground about five hours into the trip (over mountain passes in Colorado) the rig (TV and AS) started pulsing when the brakes were applied lightly; applying them harder stopped the pulsing. I was using the same brake controller gain setting I used without any problems last year. I stopped a couple of times to check the brake drums and no drum was excessively hot to the touch, and all of them were warm (street- and curb side). I use my exhaust brake and lower gears on the down-sides of the mountain passes, so I'm not riding my brakes.

I tried increasing the brake controller gain setting, and decreasing it--with no success. The pulsing continued. I don't believe (but I don't know FOR SURE) the pulsing was caused by the truck's ABS due to little or no braking being applied by the trailer. The brake controller gain is usually set at 6.0; I went to 8.0 and 4.0, with no change in the pulsing. Again, the pulsing was most noticeable at low speed stops/deceleration, and went away if I pressed the truck brake pedal harder. So, my thought is that it's not the ABS; the pulsing also seemed a little faster than when they are pulsing when stopping on ice (don't know if the ABS makes adjustments for pavement conditions or not--I think it's just if it detects lock-up of the truck wheels, which was NOT happening in my case).

I usually carry about 75% fresh water, and about 20% in both the grey- and black water tanks when towing (for rear weight balance, and to slosh around in the grey and black water tanks to loosen any "deposits").



Once at the campground I have checked AS wheel lug nut tightness; none were loose, and all were within a few lb-ft of the required torque setting.


I checked brake fluid level in the truck; good.

I checked the hitch ball nut tightness; good.

I checked the receiver and pin for excessive wear; none.

I'm out of ideas here.

Suggestions? Previous experience? I don't think the braking was at all inhibited during the pulsing, or at any other time. It's like when disc brake rotors get warped and need turning--but my truck only has 26,000 miles on it, and not all that many towing miles. I set the brake controller gain by using the brake controller manual slide to stop the rig from about 10-15 MPH in a reasonable period of time without screeching (locking up) the trailer wheels. (That's how my grandfather taught me, and I don't believe that's changed in decades--but I may be wrong. I've been wrong before, and I'll be wrong in the future. Just ask The Wife. )

Thanks in advance for any advice or previous experience. I've looked through the Forums and didn't spot anything particularly related, but there are a LOT of posts and not everyone uses the same terms to describe the same phenomena....

My first thought on the pulsing is to take the truck out on it's own and run it down hill, then apply the brakes lightly. If you get any pulsing I'd suspect the rotors and they no longer turn them, they throw them away and put new ones on. Our Toyota 4 Runner just hit 30,000 miles and I know for sure we need new rotors.

If that is not it you might pull the right rear wheel on the trailer, drum and all and check for any broken parts in there. Happened to us on our 2017 Classic and although we got no pulsing we did get a banging noise and the wheel got very hot. There is a tread on it along with others who've experienced the same, all with self adjusting trailer brakes. IF you pull the hub you'll need a socket to fit the hub as well as a 150# torque wrench, but I suspect it's the truck.

[smithcreek]

I have to take one of my drums in to get it turned, it's out of round. When I jack the trailer up and spin the curbside wheel I hear the shoes graze the drum at certain points in the rotation. Is it possible one drum is out of round and the pulsing you feel is that one engaging intermittently before the others?

[overlander63]

A likely culprit is an out of round drum, or a warped brake rotor.
Try applying the trailer brakes by themselves, and see if you can feel the pulsation. If so, it's probably out of round drums

[DaveP]

I have a 2014 F150 with 36K miles on it. I mostly tow my 2004 Classic 28 in the Colorado mountains and found that my brakes were pulsing (with and without the trailer). I changed my front brakes and rotors to Power Stop Z36 Extreme Truck & Tow 6-Lug Brake Rotor & Pad Kit - Front. The OEM brakes were completely shot, pads cracked and rotors grooved. The Power Stop completely fixed the problem.

I doubt it is your trailer, but there is an easy way to check. Next time you are driving the truck around town and the brakes are good and warm, try a hard stop from 50 mph to 10 mph two times. See if you feel any pulsing. If you do, then it is the truck.

[UnklJoe]

Thanks, everyone, for the info and suggestions.


The truck does not pulsate when stopping when the AS is unhitched--either stopping hard or normally.


When using the manual slider of the brake controller to slow or stop the rig when towing the AS there is no pulsing--from any speed. (Sometimes during a steep descent down a mountain grade I will use only the trailer brakes, though I do that less frequently now that I have a diesel with an exhaust brake.) But, I did try that on this trip out.


Today, while returning from a shopping trip into a nearby town the left rear Maypop (Firestone) Transforce original equipment tire blew at about 50 MPH. Can't really see why it blew, but it went quickly and was smoking in the 1/4 mile it took to get to a turnout (slowly), and was throwing rubber. Fortunately the rim was not damaged. The low tread bars were just beginning to be visible, but was not near close to needing to replace the tires (though I was planning to when I returned after this weekend to take advantage of Labor Day tire sales....). Odd, but probably not related to the original problem.


I will have the tire shop look at the disc brake rotors tomorrow. Really hope I don't have to replace them while away from home, too. I am getting what I believe is a good deal on four tires, mounted and balanced, though not on the Michelins I was going to purchase on my return.


Thanks again for all the ideas and suggestions!

[UnklJoe]

Originally Posted by UnklJoe

Thanks, everyone, for the info and suggestions.


The truck does not pulsate when stopping when the AS is unhitched--either stopping hard or normally.


When using the manual slider of the brake controller to slow or stop the rig when towing the AS there is no pulsing--from any speed. (Sometimes during a steep descent down a mountain grade I will use only the trailer brakes, though I do that less frequently now that I have a diesel with an exhaust brake.) But, I did try that on this trip out.


Today, while returning from a shopping trip into a nearby town the left rear Maypop (Firestone) Transforce original equipment tire blew at about 50 MPH. Can't really see why it blew, but it went quickly and was smoking in the 1/4 mile it took to get to a turnout (slowly), and was throwing rubber. Fortunately the rim was not damaged. The low tread bars were just beginning to be visible, but was not near close to needing to replace the tires (though I was planning to when I returned after this weekend to take advantage of Labor Day tire sales....). Odd, but probably not related to the original problem.


I will have the tire shop look at the disc brake rotors tomorrow. Really hope I don't have to replace them while away from home, too. I am getting what I believe is a good deal on four tires, mounted and balanced, though not on the Michelins I was going to purchase on my return.


Thanks again for all the ideas and suggestions!

Had new tires (4) installed yesterday, and personally inspected the disc brake pads and rotors, and had the tire shop manager look at them as well. No issues with the pads or rotors. And the pads are barely worn; the brakes on the RAM 3500 are massively big.

Won't be able to do any more testing until I hitch up for the drive home. I will do some low-speed driving/braking before heading out on the highway just to get some more feel for what might be happening and if it happens again. The pulsing didn't start until half-way through the trip out last weekend.

[UnklJoe]

Okay, the pulsing began immediately when I started the trip home. I immediately checked the brake drums for temperature, and the streetside drums were pretty hot, while the curbside drums were only warm.


After 150 miles or so, over a couple of short passes, I checked the brake drums again--and this time the curbside drums were not very warm at all, and the streetside drums were very warm--too hot to leave fingers on for any time at all.


Fortunately, the RAM 3500 brakes are more than adequate, and the exhaust brake helps a lot, too. I reduced the brake controller gain and didn't drive over 65 MPH all the way home.


This morning I got my Jiffy-Jack out again and checked all the wheels/brakes one at a time, and the forward curbside brake barely stops the wheel from rotating when spun by hand and the brakes are applied hard from the truck. All the other wheels stopped immediately when the brakes were applied, even lightly--but not the front curbside wheel.


I could hear the brake magnet actuating on all four wheels, but the front curbside wheel just doesn't stop. I'm suspecting something inside the drum is broken or "out of adjustment." (I'm under the impression these Dexter brakes never need adjustment, but I suspect that's a lot of hype and they might need adjustment of some kind from time to time. I'll be searching the World Wide Web for information later today.)



I crawled under the vehicle and the brake cable to the front curbside brake seems to be intact. There is thick heat-shrink tubing on both of the wires connecting the sheathed brake cable conductors to the brake wires. The white wire connection, though, seems to be a little "loose". Also, the brake cable on the front curbside wheel is MUCH longer and "exposed" than any of the other three wheels.


I don't have a large enough socket to remove the wheel, so I'm going to call a local mobile RV repair truck and get them to come to the house and do an inspection and repair.


I'll report back with my findings. Thanks everyone for your help and information!

[smithcreek]

When you spun them, the street side wheels spun perfectly free, no shoe/drum contact at all?

[UnklJoe]

Originally Posted by smithcreek

When you spun them, the street side wheels spun perfectly free, no shoe/drum contact at all?

Yes; they all spun freely when off the ground--on both sides of the trailer.

[UnklJoe]

Interesting information on this thread:


http://www.airforums.com/forums/f439...ir-186534.html


I'm beginning to suspect a broken spring or self-adjusting cable.


I'm taking my TT to a RV repair shop tomorrow (don't have the 1-7/16" socket to remove the axle nut). I will ask them to take pictures (I will be on a flight to Hollywood!).

[smithcreek]

Just had my drum turned this morning at the local NAPA that's owned by a neighbor of mine. He said the drum was out of round AND did not show any bluing. Meaning, it was not warped due to overheating, but was probably out of round from the factory.

Anyway, I put it all back together and took the trailer out for a 25 mile spin. Both wheels (Bambi) now run the exact same temperature and when I touch the drums both are warm but not hot.

Before having the drums turned the curb-side drum was too hot to touch for more than a second or two. According to the TPMS it ran 6 degrees hotter at the TPMS valve cap, so I'm sure the rotor itself was a heck of a lot hotter. Good luck with yours!

[UnklJoe]

Good to hear; thanks for the feedback. I'll have the shop check the drum for roundness.

[UnklJoe]

I took my TT to an RV repair shop today, and the Tech's found the brakes (all four--but especially the curbside) we're out of adjustment. And these are Dexter Nev-R-Adjust brakes. And I just returned from towing the TT about 1000 miles. Sure seems odd to me.

However, the difference in braking is night-and-day. The rig stops extremely smoothly and much "faster."

The tech's said they didn't believe the drums felt or sounded like they were out of round, and apparently they didn't pull any drums.
This doesn't give me much confidence in the Nev-R-Adjust brakes....

[Craigq Levy]

I know this is an older post, but I have the exact same situation. What type of adjustment was done to resolve the pulsing issue?

[GCinSC2]

Craigg,

I'm speculating based on fixing one AS with a problem in the self adjusting brake system.

The self adjusting system didn't self adjust.

Reads like the fix was getting under and using the old 60's-70's drum brake adjusting tool and get the shoes back into good adjustment. A bit of drag but not very much. Dexter Axle actually has good info about brake service and adjustment info on their website. They make the axles on AS's not sure what year they kicked in but current mfgr.

Also it would be very helpful if you posted your trailer year, model and any details about the brakes that apply. Also consider starting a new thread to minimize confusion with old v new question. These brakes on older rigs were manual adj then self adjusting was introduced, not sure what year.

Welcome to Airforums.

Gary

[Craigq Levy]

Originally Posted by GCinSC2

Craigg,

I'm speculating based on fixing one AS with a problem in the self adjusting brake system.

The self adjusting system didn't self adjust.

Reads like the fix was getting under and using the old 60's-70's drum brake adjusting tool and get the shoes back into good adjustment. A bit of drag but not very much. Dexter Axle actually has good info about brake service and adjustment info on their website. They make the axles on AS's not sure what year they kicked in but current mfgr.

Also it would be very helpful if you posted your trailer year, model and any details about the brakes that apply. Also consider starting a new thread to minimize confusion with old v new question. These brakes on older rigs were manual adj then self-adjusting was introduced, not sure what year.

Welcome to Airforums.

Gary

Thanks for the insights - I'm pulling a 2018 Classic 30 RB (new to me) with a 2020 2500 Silverado Diesel