Please help me identify 5th wheel towing issue.

[ZeeLet50]

I have a 2016 3/4 ton GMC gasser with Anderson hitch connected to a 32' trailer that weighs 12.5k with about 2100lbs pin weight. When traveling I get a jerking in TV when there is a load. Happens going up a hill or slight elevation in road. Usually felt more above 30mph. I have a cushioned pin box and Morryde Cre3000 added to suspension. Is this "chunking" or do I have an issue with slipping tranny or chugging motor. Can't see tach moving. Never happens on down hills or full throttle pulls up hills. No issues noted when not towing. It can even happen on smooth roads. Its not constant but happens enough to be annoying.

[Thermoguy]

ZeeLet50 wrote:
I have a 2016 3/4 ton GMC gasser with Anderson hitch connected to a 32' trailer that weighs 12.5k with about 2100lbs pin weight. When traveling I get a jerking in TV when there is a load. Happens going up a hill or slight elevation in road. Usually felt more above 30mph. I have a cushioned pin box and Morryde Cre3000 added to suspension. Is this "chunking" or do I have an issue with slipping tranny or chugging motor. Can't see tach moving. Never happens on down hills or full throttle pulls up hills. No issues noted when not towing. It can even happen on smooth roads. Its not constant but happens enough to be annoying.

I have a similar truck and trailer setup - 2015 Chev with Duramax. I assume you have a standard (short) not regular (long) bed. I have the short bed. I also have the B&W Companion and have looked at the Anderson. The reason I haven't switched is because when I first got the 5th wheel the chucking was awful. The B&W has a lot of adjustments and I experienced with a lot of them until I found a comfortable position for the hitch. I believe this was the majority of my problem. I still get some chucking but having a full tank of fresh water helps it to pull smoother. It seems that my rig might be nose heavy as the fresh water is in the back so it would lighten up the hitch. I think the chucking comes from the short wheelbase.

[mapguy]

To check if trailer frame is parallel to ground. Find a flat level spot for truck/trailer. Measure main rails (not fifth wheel platform portion of frame) of frame aa far forward as possible to ground . Then measure main frame rails to ground, as far back as possible. If frame is in the proper position -both front and rear measurements will be nearly the same. Much more than an 1" higher front measurement compromises suspension travel of rear axle. Lack of suspension travel amplifies the normal push-pull of a fifth wheel hitch system.

[ZeeLet50]

smarty, we usually travel with about 10 gallons of water to flush toilet when traveling and other emergencies. mapguy, it appears level but will recheck. I had to raise ball on hitch one hole to deter damage to my toneau cover rails. I can raise the pin box up one hole if needed. No helper springs on truck yet but it does sag at least 2" to level
as GM's sit ass high to start with. Have not checked weight yet to verify pin weight. Maybe this weekend i can find a place.

[mapguy]

Classic signs of 2 potential issues.
1. trailer/hitch/truck set up has trailer nose high. Trailer frame should be parallel with ground (level ground for checking). Having the trailer nose high reduces rear axle travel. Nose doesn't have to be very high to affect suspension travel negatively on a leaf spring suspension.

2. Pin weight - typically good ride has pin weight at or above 20% of actual trailer weight. Mine rides best with ~23% pin.

you don't need helper springs or such if the truck does not sag at the proper pin weight.

Edit: Are your factory overload springs staying fully engaged while towing? if not the symptoms you describe will be present.

[smarty]

if you are travelling your water tank either needs to be completely empty or completely full. A partially full water tank could cause your chucking issue?

[4x4ord]

When I have my 800 lb motorcycle on the back of my 5ver I put 400 lbs of gravel in the front closet to gain a little pin weight. It helps immensely.

[94-D2]

This may or may not be related to your problem, however I will relate my experience with a similar situation.

I have @ 99 Dodge Ram Cummins 2500 with the 47re transmission. I had it heavy duty built for pulling with a triple plate torque converter. Is was so strong that I was warned to be carful when the converter locked up because it will break a shaft if your foot is I. It under a load. My problem came when I would climb a grade in over drive and locked. It would chuck, or buck like an engine miss but without the sound or the tach showing it. I learned that if I backed out of the throttle and got out of overdrive, the bucking would stop. I eventually learned that the condition was the torque converter slipping against the plate while in the locked position with a load on it. If I full throttled the rig while it was chucking, it would downshift out of locked and stop. However, if I stayed in it, I would end up going way to fast and That creates all sorts of other problems.

The answer to this problem is to increase pressure in the transmission to create greater physical contact against the plate while in lock up. Only way for that to happen for the 47re is to replace the entire throttle body with an after market and install a switch and fooler board to lock out torque converter lock up. I could do all that but I would effectively be building a manual automatic and further complicating the operation of my exhaust brake since it needs the torque converter lock up to operate. The cheap fix is to lock out over drive and go 50-55 mph up the grade, With 4:10 gearing in my rig with the gearing of the 47re, it is painfully low geared for the highway and very hard to only use about 1/4 throttle for that long a distance. Plus those rpm’s are tough on that Cummins which loves to run at 1800.

Food for thought. I suspect the transmission in the right path to your problem. In either case, the process of elimination is they way to figure it out. Start with the no cost options of elimination and work toward the costly.

Good luck with it.

[garyp4951]

I don't think its the tranny, because I experienced the same thing years ago with a gas truck pulling a heavy load. It is a pulsing surging feeling that only stops when you back off the throttle.

[ZeeLet50]

Super_Dave, feels like its coming from the back and I have suspicions that it might be somewhat to do with the trans. I only have 26k on the truck. Was going to have a full fluid change out to synthetic but $300 is pricey. ependydad, not ready to ditch the Andersen yet. I love the fact that its easy to hook up and lightweight.Want to exhaust all possibilities first. I plan on getting the rig weighed to help troubleshooting.

[ependydad]

My experience with a pin light fifth wheel (15.5% measured) and the Andersen was exactly as you described. It was a nightmare for us and we ultimately replaced it after just a couple of months. It caused my wife significant pin while towing.

I first towed that setup with my B&W Companion and didn’t experience the same jerkiness. I traded that out for the Andersen due to the weight of my trailer (21k) vs the ratings on the B&W (20k for the post version).

I went crazy and switched to the TrailerSaver TS3. It’s comically heavy but the full air ride hitch is amazing.

Longest story shortest: ditch the Andersen.

[Super_Dave]

Does the jerking feel like it is from the front or back? On uphill on ramps I get heavy jerking from my torque converter and gear shifts.

[humblerb]

My GUESS would be that you are a little nose-high. When you head up a hill, the back end drops and the front raises. I'd suggest checking your level when hitched up. Need to be slightly nose-down, rather than slightly nose up.

[ZeeLet50]

thomas201, if you drive for 3 or more hours with the fore and aft jerking, it gets old. Sometimes it makes my dog sick and she pukes. It only hurts the body not the rig. LOL

[thomas201]

Since it hurts nothing, just ignore it.