help, 82 truck bed trailer death wobble (1 Viewer)

[cutnchopit]

So I finished the basic construction of a truck bed trailer with utility topper for camping. Then I took a job a few states north and had to move suddenly without taking it with, just went to pick it up on a trip home and had to leave it because of death wobble and a ten hour trip(slower back roads route).

Info:
82 toyota pickup long bed

Hitch receiver and pin with 2" square .25 wall tube tongue about 5' and 2" ball reciever?

5150 bilstein shocks with slightly higher and lower mounts than stock

Stock leaf springs

88 ifs width axle housing

put on taco/tundra spare wheels/tires for the trip(had 35" bfg's)

Aluminum utility topper with double doors

Had an exo cage for a 1st gen cab strapped to the roof of the topper around the front

So heres the scenario,
It was being towed with a 2wd 98 4runner, havent ever driven it more than a few miles and at that time the suspension was too soft with lots of body roll, no shocks and 35 bfgs. so before the trip I added the shocks, ifs axle housong and had th 4 35s in the back with some tubs of camping/fishing stuff.
It towed fine but swayed a bit still (top heavy side to side not left to right) Get to the house and my step dad talks me into switching the hitch a little lower, im thinking a little more tongue weight and slightly pitched down. We switch that in the evening and i replace my 5/8 bolt woth an actual 5/8 hitch pin.
At 4:30am I head out to get gas, all is good hitting a few bumps and normal top heavy sway happens, but then a different type of bump nothing seemed differeny about it except it gave it a violent left to right death wobble until i slowed and it went away. I was going about 35-40 and slowed down to 15 or less to stop it. Get gas, go back and dump the tires at my folks house and leave the cage strapped towards the front thinking less loaded suspension might help, with more of the weight to the front with the cage. Maybe, no death wobble?

Go the same route and speed to see if it wobbles again and it doesnt. Next road, it does it again. Stop and strap down the suspension a few inches with giant ratchet straps to see if that helps. Minimizes the body roll but a little further down the road and it does it again.

So im having a terrible morning now for this and a few other reasons and I throw/in the towel. Tow it to my sisters house on my way out of town. Going through some road construction on the way and it pulled fine with very little top heavy/suspension wobble since strapped and no death wobble! Strapped and lighter load.

 

[cutnchopit]

So from what little ive found online, possible issues would be different tire sizes or pressure, bent tounge, too light of tongue weight, bad bearings, bent axle, shifted axle and..

What I haven't tried is to see is if the bolt I had holding my hitch in the reciever was preventing some left to right play that the pin does not, and that wobble leveraged with the trailer made the death wobble, or similiar idea with the tongue mounting to rhe trailer via hitch and pin

Didnt check tire pressures but it wasnt a dramatic difference

Dont know if the tongue being too long or short would effect it, too much flex in a single tube tongue vs A frame tongue, to top heavy in nature, truck tires vs trailer tires really matters but then how would you get offroad tires? I also have a hitch in the back of the trailer so maybe towing with the bed backwards could change things, shackle would be up front and could change weight distribution a bit?

Anyone else have a death wobble Trailer issue, truck bed trailer issues towing. Wanted to get it up here to tinker and figure it out by trial and error but not I need to figure out what it is to get it home.

Thanks Guys,

Ben

 

[ntsqd]

A picture of the trailer would be good. My guess is too much bed aft of the axle and not enough forwards of the axle. That is pretty common with pick-up bed conversions that use a something other than an 8' full size bed.

Every tow rig / trailer combo has a "Critical Speed", the speed at which the trailer will sway and there is nothing that you can do to stop it other than slow down. Tongue length is the single largest factor in the trailer stability equation (such an equation does exist - called the "damping ratio", and it would be hard to type it in here). The longer the tongue the better. A heavier tow rig may help.

 

[cutnchopit]

Thanks, just reset my phone and forgot to post some pictures when I got off shift. I'll try to get some pictures up asap. I'll look on my photobucket for pics when I was building in the meantime.

 

[cutnchopit]

this was before I cut it I think, tongue should end right at or before the end of the picture.

The top was my first thought on tongue mount but went with a lower, heavier wall hitch.

 

[ntsqd]

What needs to happen, and I'd be the first to say it ain't gonna happen if it were my trailer, is to swap the bed 180° on the frame. Then the fore/aft weight distribution will be much closer and much harder to load wrong.

If you have a spare and it isn't mounted up front now, it should be. Any other permanent mods need to be mounted in front of the bed.

 

[cutnchopit]

There is a hitch I mounted in the rear of the bed. For future accessories or to be able to tow back out of somewhere in a pinch without turning the trailer or any randomness from life happening. planned for a spare tire on the tongue later on as well as a beefy jack/stand. It has two (empty now) locking 5 gallon fuel tanks mounted there. But thats all once i get it from florida to tennessee and can tweak and refine as needed. I havent tried towing it in reverse, would the shackles forward cause any weird handling issues to tow backwards? I may have a few hours to tinker since im down for thanksgiving but not attempting to tow it back this time. Thanks

 

[gsdog2]

Mine is similar....only on a Datsun bed/frame. Was hauling butt on the highway fully loaded and always tracks nice and tight. I have a truck tool box ahead of the bed and just as it turns out, the wheelbase from the trailer axle to cruzers rear axle is about the same as the cruzers wheelbase. Don't know if that has anything to do with wobble.

 

[cutnchopit]

found the picture I snapped after welding on shock mounts with raised hitch shown, vs straight hitch when I had death wobble.
before I went and picked up the roll cage which went around the front of the topper, tongue side.

 

[cutnchopit]

Well its fixed now but I did a few things at once so I cant say it was one specific thing. When i picked it up to take to a buddy's shop i was surprised with how much play I had in the tongue with the hitch pin mount. So my assumption is that With a good hitch shim to prevent left and rigt play, it would probably be fine and still allow for the removable tongue. But making sure i had it ready for the 460 mile trip and ome opportunity to work, I pulled the hitch tube out further and welded it on each side of the reciever. Then welded some square tube from the corner of the frame to the tongue and then welded the hitch to a thinner hitch that was mounted above (meant for a removable cargo rack/bike rack or something like that). It then towed like a dream and with a hitch shim in the trucks hitch t was really smooth. But then I loaded down the trailer with an exo cage, go kart, some steel plate, scrap steel bin and my tool bags, so I strapped the suspension again to prevent any over loaded sway/roll from the suspension just in case. I can post pictures another time but probably not necessary.

 

[Trollhole]

Usually a trailer that sways back and forth is due to low tongue weight. Which can be fixed by moving the axle back or adding more weight towards the nose.