Front end bounces horribly when going over 55 mph

[tbchristian3]

Hello everyone, 

I have gone through most of the posts for cab over bouncing and I can't seem to find a solution that fits my current set up. 

I have a 2015 GMC Sierra 1500 5.3 L V8 4X4 Crew Cab.

The slide in camper is a sun lite pop up but I am not sure of the model number or exact weight. Unfortunately the guy I bought it from didn't have any info on it. He said he though it weighed roughly 1000 lbs. 

What I do know is the camper only sticks out a few inches past the tail gate so it's roughly 6ft long inside the bed. My bed is the 5.5 ft (the shortest bed they have in a 1500). I have the Happijac camper tie downs installed in between the cab and bed and tie downs mounted to the back bumper. I used a regular set of turnbuckles off of amazon. They are Brophy Machine Works brand and have a tensile strength of 2100 lbs.

The issue I am having is that when I get up to 55 mph or higher the front end of my truck starts to bounces uncontrollably. I have tried adjusting tire pressure and tightening the turnbuckles but neither of those things helped at all.  Any other pointers? is the camper to heavy for my truck? Is it a WD problem?

Here's a pic:

[Grit_dog · Accepted solution]

Not likely the issue at all. 
I feel like I asked a couple few questions you haven’t answered. As have others. 
what’s under it for suspension?

what you got for tires and pressure?

what kind of road, asphalt or concrete?

how long how far how many roads and miles have you driven it? Or any other heavily loaded truck?

I can get an almost empty truck bouncing pretty good at the right speed on the wrong concrete highway. Yet never had even a severely overloaded pickup bounce like that on smooth asphalt. Concrete panels create ridges at each panel joint where they’re saw cut, when the edges swell or curl. Sounds like what you’re experiencing, but until you provide more insight, can’t tell. 

[stevesgarage]

The first thing I did to my 3/4 ton truck when I started carrying a 2000 lb slide in camper was to install air bags in the rear suspension.  They can be inflated/deflated with an on board compressor and dash mounted gauge.  Any ride problems can be instantly corrected to adapt to road conditions!

[user113]

It seems you have never gotten your rig weighed before.

Go to the cat scale locator page  and type in your zip code.  They're all over the place.

Drive there with your camper fully loaded like when you have previously experienced the issue.  If possible, take back roads so you don't have to drive 55 mph or faster. 

1. Find the scale, and hopefully there will be a spot nearby where you can unload and then re-load the camper.

2. Unload it, drive your truck onto the scale and get it weighed.  Make sure your front axle is on one pad and the rear axle is on a different pad.

3. Go pay for your weight ticket (last time I did this it was $13).

4. Then go reload the camper on your truck, drive back onto the scale and get a "re-weigh."  You'll need to know your previous Weigh Number.

5. Go pay for your re-weigh ticket (last time for me was $3.50).

6. Then go home and post the results of the two tickets.

Your weight tickets will show you the "steer axle" weight, the "drive axle" weight and the "gross weight."  Post the data from both tickets.  Once you post solid date, we'll be able to advise you much more better.

[opnspaces]

I know it was suggested before. But I would go to Home Depot and buy two or three 50 pound bags of sand and save the receipt. Put the bags on the front passenger floor and go for a drive to test. Does putting some weight up forward alleviate the bouncing? After the Test take the bags back to Home Depot for a refund.

[Diamond_c]

I’d suggest air bag suspension system, or overload springs front and rear. Heavy duty shocks all around, and 10 ply tires. If that don’t fix it the only other thing would be to buy a 3/4 ton truck ( aka 2500 / f250 ) to dedicate as a tow vehicle just for the camper.

[Ray_IN]

Bouncing is usually worn-out shocks.

I would locate a scale and weight both axles, 4-corner weights would be ideal.  That tells if your truck loaded weight is balanced or the front axle is way underweight.

[tbchristian3]

I have considered just looking at replacing the front shocks in general. I am sure they haven't ever been replaced and the truck now has over 100,000 miles on it.

[stevenal]

I see a big back seat well ahead of the rear axle. Was the seat loaded during your test run? Consider upsizing your human and/or canine family, or use the back seat to store heavier equipment and extra water.  It's not the camper COG that matters so much as the payload COG. 

[Bedlam]

Like was posted, get axle weights when loaded and unloaded to see if the front is getting lighter with the load added. Adding water to the fresh tank or loading all your heavier items forward of the axle can help equalize some of the weight. Adding heavier damped shocks to the front and rear and will reduce oscillations. If you are worried about unloaded drive comfort, look for something like the Rancho RS9000XL than can be adjusted with a knob based on load. Stiffening the rear will marginally help the front bounce, so I don't advise that unless you are getting a lot of spring bounce in the back when driving due to soft spring rates. The Torklift lower StableLoad wedges are a good option since they can be engaged or disengaged based on load.

[Grit_dog]

If that pic is on stock suspension, that camper is pretty light and definitely not too heavy for the truck. 
what you’re describing sounds like driving on concrete pavement and the pavement joints making the front bounce. 
How far what kind of highways have you driven on?  Does it do it on asphalt too? (Likely doesn’t). 
Regardless, heavy duty rear shocks and stiffening up the rear suspension assuming it’s still just stock will help everything in general. 
Maybe describe the bouncing and conditions better. Pursuant to what I asked above. 

[tbchristian3]

The bounce was on multiple highways on the way home so asphalt and concrete here in Texas. I drove roughly 40 miles on mixed type roads. Highways, access roads, residential ect. The bouncing was only at 55 mph and over so I only felt it on the highway. I did also try to go faster and as I did it got worse so I had to slow way down to get it to stop. I am not sure if the camper is bouncing down in the back causing the front to lift. It's hard to tell while driving. Shocks on the truck front and back are stock from the factory so I am sure they aren't that great.

[notsobigjoe]

Well, these opinions are all good and sound advice for the problem your having. Grits advice is where I would start. Suspension. I would check the front ball joints before investing any time or money into what looks like a great rig. Tie rods too. Your truck is driving great at speed but as soon as you go over a certain threshold it starts acting like you need some front end work.  The rear weight is kicking in when you go over 55 lifting the front of your truck off of any pavement which occurs with all truck camper rigs I think it would expose the front end issue.  Especially on such a light TC'er load. It's your money... Cheers, Joe

Good to see you Grit....

[tbchristian3]

Thank you. I am definitely going to get the front end checked and look at the front and rear axle weight like Grit mentioned.

[Grit_dog]

Not sure I mentioned axle weights. That can be approximated easy enough but it may help you to see actual scale numbers. 
Beyond that, you need to answer more of the questions that I and others have asked. 
you identified shocks, possibly. They could be shot or they could be fine. If you can’t tell the difference by how it rides and handles then easy to remove and see if blown or not. 
Tires and rear suspension, you haven’t answered but that’s where I’d be. Given your lack of succinct responses I’m guessing you don’t have heavy duty tires and sufficient pressure / load capacity in the rear and you’re just on soft stock springs only. Again that’s the stuff I’d hone in on. 

[joerg68]

That is why I would start with weighing the axles. Then he knows the actual numbers, which may or may not be within reason.

If it is "just" porpoising, there is indeed a lot that can be done.