Rapid trailer jerk at higher speeds

[GreenbackHunter]

I'm having trouble with my boat trailer.
When I reach 40 -65 mph, the van jerks very rapidly and hard, making it unsafe and uncomfortable.

I have a 2005 Buick Terraza, same as a Pontiac Montana or Chevy minivan, Same body, same frame.
And an 18 1/2 Smokercraft on Shorel Landr trailer.

To start, my last van was the same model, and had no issues. Same hitch on this van.
Curt Class III...

When loaded,, ready to go, my tongue weight is about 15%, trailer sits level, no excessive play on hitch, receiver, or 2" ball.
I haven't changed the way I load the boat, other than a few empty coolers strapped down, once in a while, to save room in van.
And van is basically loaded the same, every time.
One thing to note, is that the boat and trailer did sit, for the 2 years, when covid hit.
I thought it might be a flat spot on tires, from sitting, but that should affect it all the time, not just once a trip starts, with full tank in van.

When I start a trip, full tank of gas, the trailer starts Jerking so fast and hard, I have to slow down. This starts at about 50 mph, and don't stop unless I slow down to about 40, 45.
After about 1 hour of driving, it seems to go away.

I've checked trailer wheel bearings, has good tires, bought new, 2 years ago, low mileage, and nothing has changed, since I used to tow with old van. I never had this problem.

I've had a great auto shop, go over the van, and nothing is wrong on van itself.

The only thing I can think of, is weight distribution, or angle of trailer to van, when I have a full tank of gas.
But, when the gas tank is full, it looks perfectly level.

Any ideas will be greatly appreciated.
This is dangerous, and getting annoying.
I have to stick to back roads, until van and trailer feel right. I have a few big trips coming soon, I'd like to get this figures out.
Please help,
Thanks

 

[dingbat]

Tires could be out of round. Would take them in and speed balanced to remove tires from the possible causes

 

[Earl Cordova]

Tires could be out of round. Would take them in and speed balanced to remove tires from the possible causes

Good idea.
For some reason lots of people never have their trailer tires balanced.

 

[bruceb58]

How heavy is the trailer? Does it have brakes?

 

[airshot]

Jerking or swaying?? Many folks get these mixed up when their trailer goes haywire. From your description it sounds more like a sway issue. Many times additional weight must be used on the tongue to cure this issue. Many folks never check there alignment of their trailer wheels as well as balance. Have seen more than a couple trailers crabbing going down the road...hope you find your issue......

 

[GreenbackHunter]

Thanks for the fast replies.
Boat and trailer, even when loaded only weights about 1600 lbs.
Single axle, no trailer brakes, just simple, 18 1/2 ft. aluminum boat, 65 hp motor, and trailer.
Boat specs at 700 lbs, motor about 300 lbs, trailer, I'm estimating at 300 lbs, and roughly another 300, between batteries, and gas tank, etc.
I'll try to find a scale, just so I know, but I have to be within 150, 200 lbs, of my figures....
And, I don't load anything in the boat, except for a few empty coolers, to save space in van.

I've dealt with sway, and mis-aligned axles before, on other trailers, but never felt anything remotely lie this.
I did pull wheels, cleaned and checked wheel bearings, as I used to be a mechanic.
So wheels, bearings, and spindles are good, and torqued right.

It is a rapid jerk, starts at about 50 mph.
Jerks forward and back, so hard, and fast, it jars me in the driver's seat.
Thought it was the road, at first, but tried different highways, and back roads, get the same result.
Just stumps me, because the last van I had, was the same model basically, just a different name, as GMC/Chevy does. Never had an issue, it towed nice and smooth.

I load everything the same.
Not much added weight, just me, dog, and basic fishing gear for a week. No loaded coolers, I shop at my destinations...
When loaded and ready to go, it's loaded the same way, all the time. I keep added weight in van and trailer to a minimum, and balanced.
The Chevy Uplander, Pontiac Montana, and Buick Terraza, are all the same body.

There is a lot of play between receiver and hitch, but it was always like that. Never had an issue before.
I did find a leaky air line on my suspension leveler, causing the rear of van to sit low, and obviously, hitch follows suit.
But only about 2 inches below level.
I'm gonna start with fixing suspension leveler, and have trailer tires checked and balanced.
Suppose it is possible to have flat spots, since it sat about 2 years, in the driveway.
But, if that's the case, why would it go away, after driving roughly 60 miles.
The only thing I can think of right now, besides tire issue, is when I start, there's a full tank of gas, further dropping the back of van.
Then again, when I left home, I had a full tank, and didn't have a problem.
The last 2 trips, only 2 so far this year, the problem only started once I left Winneconne, WI.
It didn't do that either time I left from home.
It's 200 miles, each way.
Jerking goes away, after about 1 hour on the road.
I've tried 3 different roads, once I left for home, and always does the same thing.
If it's a tire issue, why would it stop after a while ?
I will have them checked, just to eliminate the possibility.
Go from there.

Was thinking about moving axle to next place back, try more tongue weight, but think that would put me over 20%.
I'll try moving a 75 lbs battery up front, out of the back of boat, for a while, see if anything improves. That should be enough shifted weight, to make a difference.
A simple experiment, I can change in 10 minutes.


Would the back of van, riding too low, due to bad air suspension, cause this ?
I'm having it fixed, but won't go to shop until end of this month, when I can be without my van a few days.
Thanks for the responses, I'll keep you posted.
Might take a short trip this week, back to Central WI, just to see if I can solve the problem, before I take longer trips to Northern WI, and MN, later this month.
I've never experienced anything like this,
Thanks for all the help.

 

[briangcc]

Long shot but..... on my first Tundra my emergency (parking) brake was hanging up. IF I used that I could launch/retrieve with no issues. But about 10-15 min into a trip, it'd start jerking pretty decently to the point where I had to pull off, reset the brake and all was well for the remainder of the trip.

So....are you using your e-brake and if so when was it last serviced?


Other option....that boat is rather small where a different mini-van/xuv/suv could pull it. Any chance you could hook the trailer up to another vehicle to see if it exhibits the same problem??

As for towing tongue down....you don't have trailer brakes so probably not much difference. You could try using a different drawbar to raise your trailer up to see if that corrects it. Cheap enough to do.

 

[GreenbackHunter]

Yes, use parking brake, every time st ramp.
And loading boat is the last thing I do, other than fuel van, before hitting highway.
I don't get a lot of time on the water, so when I can fish, I stay to the last possible moment.
That would make sense, where jerking goes away, an hour into trip.
And, both times it happened, it was when I left for home, never did it, leaving my house.
I'll pull back drums, check parking brake, asap.

I didn't think a minor down angle would be an issue, and did try another hitch.
But, I'm at a 9" lift now, the other hitch I have Is also a 9", maxed out lift. Same problem.

My brother due back this weekend.
Has new, Silverado, trailers 1500.
I'll try to get his truck for a night, give that a shot.
Storms hit last night, have some clean up, so may be a few days before I get to work on anything here.

Just to give an example, when it does jerk, it feels like a blown out tire, at 50 mph.
That rapid jerk, but much harder.
Has me boggled, because I've town many trailers, in various cars, P/U's, and even 26,000 lb dump, with end loaders on trailers....
Never seen a problem like this.
And the fact that it goes away, after a while, and hasn't done it when leaving from home, makes it even harder to pin point.
The way I load, and distribute weight, in van ,and boat, to and from, doesn't vary much.
I've experienced anything else that can happen.

I'll start with easiest and cheapest 1st.
Check van brakes/ e brake, try another tow vehicle, then go from there.
Although having trailer tires checked and balanced, will help put me at ease, on long trips.
As I mentioned before, used to be mechanic, so I keep up on maintenance, do pre trip preps.
I've managed to avoid any problems, making trips fun, until now.
Just hate leaving, almost knowing I'm gonna have an issue, once I'm on the road.
I'll keep posting, until I find the problem...
Maybe help someone else in the future, since I had a hard time finding info on this.

 

[airshot]

Try adding more weight to trailer tongue, easy try and being overly heavy is not an issue but being light can be. Your on the right track in your plans....I have saw cheap tires get bad flat spots on them and after a run, mabey 1/2 to an hour they will round back out. Checking that E brake is also a good idea!! Gonna bet you will find something fairly simple to cure it. Please let us know what you find....

 

[rustybronco]

See if there are any technical bulletins on the vehicle for trailer hitching. Might be an issue with trans hunting because of road speed or engine load.

 

[GreenbackHunter]

I managed to check E brake, checked front and rear brakes while at it. All seemed fine, tho having 2500 miles of planned trips coming this fall, ceramics will be going on soon.
Have a chance to hit a local lake tmro.
I'm gonna try throwing 100,200 lbs more, in front of boat. Then try shimming the receiver, if it continues. Don't think that's a problem, but I'll check it off the list.
Also, I'm gonna try to find a scale locally,
so I know what gross trailer weight actually is.
Just tossed house scale under tongue.
Says I'm at 220 lbs. But will try adding weight tmro. I can't see that package weighing more than 2000 lbs... My guess is 1600/1700.
I'll keep trying different things you all recommended, as I mentioned above.
And tmro, I'm gonna try to stay in van, when launching and retrieving, not use the Parking Brake, since I have another experienced fisherman going with. I'm usually alone, or with someone that " knows what he's doing !!! ", tho never owned a boat in his life. Lol
Keep you posted.
Worst case, if no improvements after playing with tongue weight and checking/balancing trailer tires, I'll pick up some new bearings and races.
I did clean and grease them this spring, seen no wear, but my guess is that they're the original 1981 bearings. I'd feel better knowing they were new, before venturing into the Northwoods.
Thanks everyone.

 

[briangcc]

I'd be hooking it up to another vehicle to determine where the problem is before tossing more time/energy/parts in the hopes of stumbling across the solution.

U-haul rents trucks with hitches if you don't have a neighbor/buddy/pal/family member with a vehicle with a hitch.

And...I just re-read the entire thread. IF I'm reading it right...the last time this towed properly was with ANOTHER vehicle, not this one correct? I keep re-reading "old van vs this van". That may very well be where your issue is. Which again, hooking to a different known vehicle would help rule in/out.

 

[Scott Danforth]

double check your tongue weight

your boat looks like its sitting too far back

move your fuel tank and spare wheel to the bow of the boat.

 

[GreenbackHunter]

Yes, I'll definitely try another tow vehicle.
My brother is due back in town this weekend.
The only problem is that this has never happened when I left from home.
It's only happened the 2 times I went put of town. Drove 200 miles, loaded boat on trailer, and left to come back home.
It's only done it right after leaving the boat ramp.
I load boat, stop for gas, then hit highway.
And I've tried coming home, 2 different ways. Happened on both roads.

Yes, I know it does look like it sits back too far.
It was like that when I bought it.
And looks like they had boat further back once before.
There's indentations on bottom of boat, about 6 inches in front of the transom, from it sitting on rollers. Maybe why they moved it.
I le where it sits now.
the back rollers sit right under transom,, so weight is on that,, instead of weaker spots.
I'm going fishing, about 60 miles away tmro.
I usually lay spare, seats, and cooler next to console, and strap cooler down.
I'm going to try moving battery, fuel tank, and a spare, full, fuel tank in the bow.
See what happens.
It's just hard to get away right now.
I'll post later this weekend, after I experiment with tongue weight.
I'll let you know what happened.
Thanks for all the suggestions.

 

[Scott Danforth]

also, if the aft shocks on your SUV are at all worn, the boat will wag the car.

 

[rustybronco]

"

I have a 2005 Buick Terraza, same as a Pontiac Montana or Chevy minivan, Same body, same frame.
And an 18 1/2 Smokercraft on Shorel Landr trailer.

To start, my last van was the same model, and had no issues. Same hitch on this van.
Curt Class III...

Same year axle ration and transmission?

Parking brake recall 05V287000
"WHEN THE PARKING BRAKE IS RELEASED, THE DRIVER MAY NOTICE UNINTENDED BRAKING WHEN ACCELERATING, DECELERATING, OR COASTING, AND A NOISE COMING FROM THE REAR OF THE VEHICLE. UNINTENDED VEHICLE MOVEMENT COULD OCCUR INCREASING THE RISK OF A CRASH."

 

[GreenbackHunter]

Thanks for the recall info, I'll check with a dealer. See if it was ever fixed on this.
And, the rear shocks are leaking.
Has the dreaded air suspension/leveler.
But, the pump does keep up with it, while engine running and while driving.
Looking into replacing with regular gas shocks asap.
Says there is a kit for doing that.
I'd rather have Gas shocks.
Always had trouble with air shocks and leveling systems, on every vehicle I've owned with them.
A little different situation, but I have much more weight in van, during the week, when all my tools are loaded.
I pull them out, for trips. So there's less weight in back of van, even with trailer attached.
I'll start with the easiest/cheapest tmro.
Try shifting some weight to the tongue.
Finding actual trailer weight, on a scale.
And checking on recall.
I'll post what happens Sat night or Sunday.
Thanks

 

[Scott Danforth]

And, the rear shocks are leaking.
Has the dreaded air suspension/leveler.
But, the pump does keep up with it, while engine running and while driving.

doesnt matter if the air comressor is there. the shocks lost all dampening function

 

[GreenbackHunter]

Yes, some reason, I lacked common sense for a minute.
Shocks aren't doing a thing, if they leaking. Lol
I'm near O'Hare Airport.n
Went to IL, Fox Chain o Lakes, early Sat am. About 50 miles each away.
I put my kicker, 9.9hp(which I didn't have with before), extra full 6 gal gas tank, extra group 31 battery, and spare tire, in bow of boat.
Was a 1 hour trip, each way.
Started jerking forward n back, on my way out... after about 20 min. Wasn't as hard, but did happen.
Road had slight and long incline.
Was fine on local roads, and Tollway, even at 65 mph.
Acted up, once, after a stop light, when I hit 45 mph.
Lowest speed, that it's happened yet.
Only did it at 50, 55 mph, everytime before.
Felt it start, I accelerated hard, not causing a downshift, and it went away, in seconds.
Never did it again, that trip.
And, I did use Parking Brake, both times at ramp.
I can't get it to act up, unless I'm towing boat.

The more I think about it, every time it happened, has been on an up hill run.
Even tho none of them have been that steep.
I'm starting to think it's in the van, under a load, at certain speeds.
Possibly a throttle position sensor, going bad, or something similar.
Just hard to pin point, because I don't get out, that much, and it's random.
Tyring to go out again this weekend, not sure yet. If possible, I'll borrow another tow vehicle asap, see what happens
So, I won't post anything, until I get home, after next trip.
But, for most part, seems like added tongue weight did help.
Even though it still acted up, it was slight, and I was able to stop it by speeding up a little.
I can't wait to get on a scale, and see exact trailer weight.
Until then, I'm only guessing at trailer and tongue weight.
Before my long trips, I will have shocks replaced, find my actual weight, find proper tongue weight, have trailer tires checked and balanced, and want to replace bearing seals, they leaking a little. So, I'll have hubs off, clean and replace bearings.
I did clean and pack them, once I pulled tarps this spring, sense it sat about 2 years, thru the covid ordeal. Everything looked perfect in there.
Let you know results, after next trip.
Thanks for the suggestions.

 

[jimmbo]

Hmm, a 73 Johnson