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Old 11-02-2018, 11:26 PM   #1
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Dancing truck while towing

So I find it annoying as hell. The road conditions are crap. Have a WDH installed and working well. But when I hit a road pothole the truck likes to jump all over the place. What I mean is, I can get a serious porpoising effect, or a jump of an inch. Never loose control, but it can make you seasick from how it moves at 60 mph speed. RV trailer is 5000 pounds. Tundra truck has 7000 pounds towing capacity.

Shocks are all over 100k miles on them, but unloaded the truck rides fine.

Could just be the roads I suppose. Air pressure is good in all the tires.
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Old 11-02-2018, 11:29 PM   #2
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Slow down?
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Old 11-02-2018, 11:31 PM   #3
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Slow down?


Trust me I do!! Lol. My speed can be 45mph to 60mph, on roads with 65 to 70 mph signs.
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Old 11-02-2018, 11:39 PM   #4
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You say WDH is working well. If the truck is dancing, why would you think that? Perhaps you should have somebody check the WDH.
I expect you'll be hearing shortly from others recommending heavier springs or air bags for soft rear suspension on Tundra.
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Old 11-03-2018, 01:56 AM   #5
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Shocks are all over 100k miles on them, but unloaded the truck rides fine.
Kevin, with 100K on the shocks they've got to be close to the end of a useful lifespan. I'd be replacing those just as maintenance for a wear part and see if that takes care of it.
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Old 11-03-2018, 04:37 AM   #6
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also, make sure your tire pressure is pumped up to something suitable for the actual load on the truck axles.

but yeah, I'd be checking that WDH, ensuring its set properly. load the truck, measure the spacing from top of tire to rear fender and same in front, hitch up with the WDH and measure it again... the rear shouldn't sag more than about an inch more than the front if the WDH is properly setup. the front absolutely should not be going UP, or going down more than the rear, or the WDH spring tension is all messed up.

On my Tacoma TRD Offroad, I had a lot of porpoise action, a WDH stopped it dead, but so did properly adjusted airbags (which I got for carrying heavy loads when not towing, but they turned out to massively help while towing. also better shocks (bilstein 5100) helped the ride quality a lot.
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Old 11-03-2018, 06:23 AM   #7
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That's heavy for a FGRV, seems only Bigfoot approaches that weight. You might check that you are within cargo weight limit, got to be a heavy tongue. At that mileage you may need shocks. Check that you have LT tires, not P. Even optimized you may be pushing the limit with a Tundra.
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Old 11-03-2018, 07:51 AM   #8
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I had similar issues when towing with my 1999 Dodge 1/2 ton V6 truck
( similar mileage)
Local Mechanic said shocks were bad and suggested I replace them with heavy duty load leveling shocks ( cheap & fast & simple)
It did make the truck ride better when towing and they weren’t too bad when not towing . I eventually came to the conclusions that some vehicles tow well and others don’t and dumped the truck
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Old 11-03-2018, 10:48 AM   #9
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What's it like on concrete roads with expansion cracks every 6 ft or so?
Does it get into a steady bounce? That is called "Natural Frequency" A combination of the spring rates and geometry of the whole rig.
Contributing factors can be: too much air pressure in the trailer tires, a loose hitch ball/ball mount joint, weight distribution, etc.
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Old 11-03-2018, 11:14 AM   #10
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When i had my truck, this is before i new anything about towing. little over 100,000mi,on truck. I would drive over a ripple section of asphalt and the truck would be jumping like you said. Took it in for inspection and they said shocks/tie rods were bad, i forget which. Changed them and the truck ran like new. Carl
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Old 11-03-2018, 11:30 AM   #11
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re: natural frequency... GOOD shocks tuned to the spring rate and axle weights should stop that cold.
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Old 11-04-2018, 01:36 AM   #12
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My WDH is the spring bar with chains type. Brand is PRO SERIES. Have been told that can have a lot of spring in it. And to try changing to ANDERSON hitch WDH.

So could be old shocks with not enough dampening (need heavy duty); or switch WDH.

Looks like I might be calling some trailer hitch shops to get opinions.
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Old 11-04-2018, 01:38 AM   #13
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Dancing truck while towing

Quote:
Originally Posted by John in Santa Cruz View Post
re: natural frequency... GOOD shocks tuned to the spring rate and axle weights should stop that cold.


That’s an interesting direction. So would need to find a shop that understands shock geometry/physics under heavy load.

This video shows what seems to be happening. https://youtu.be/6Z-2WKwsLTw and maybe heavy duty bilstein shocks will help with this.
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Old 11-04-2018, 10:12 AM   #14
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My WDH is the spring bar with chains type. Brand is PRO SERIES. Have been told that can have a lot of spring in it. And to try changing to ANDERSON hitch WDH.

Escape was selling the Andersen WDH. Stopped after too many complaints. It still sells the Pro Series, which is what I have used for ten years without issues.

I suspect that your WDH is not installed correctly or that the bars are hooked on the wrong link.
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Old 11-04-2018, 10:20 AM   #15
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Did I miss what trailer you're towing? Hummm, if you post that, perhaps someone towing a matched set would post and be more helpful. Because right now it appears we're throwing noodles at the wall and hoping something sticks...
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Old 11-04-2018, 12:03 PM   #16
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Dancing truck while towing

You might look at the weight distribution in your trailer. If it is off balance, it can cause these issues.
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Old 11-04-2018, 12:49 PM   #17
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Kevin,

Porpoising is a specific problem related to under-damped, low velocity compression and extension of the shocks. It is worsened by worn out shocks and/or velocity sensitive shocks.

The first thing to do is replace the shocks. Worn out or velocity sensitive shocks allow porpoising. So don't get just any kind as replacements. For instance, Bilsteins, which are very good shocks, work poorly for towing because they are velocity sensitive. Porpoising is very low velocity movement and can be outside the speed range of effective damping.

In my experience the best shocks for towing, or variable loads, are Rancho 9000 series adjustable shocks. You can tune them with the twist of a knob to be either soft for non towing or very stiff to prevent the problem you describe.

Do not just go to a cheap replacement, or to stock shocks that are designed to make the truck ride smooth when unladen. You need adjustable towing shocks.
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Old 11-04-2018, 08:43 PM   #18
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I did not notice what kind of truck you have but perhaps a set of Gabriel air shocks and a compressor to adjust the ride height and add some damping.
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Old 11-04-2018, 10:15 PM   #19
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Originally Posted by offroad View Post
That’s an interesting direction. So would need to find a shop that understands shock geometry/physics under heavy load.

This video shows what seems to be happening. https://youtu.be/6Z-2WKwsLTw and maybe heavy duty bilstein shocks will help with this.
the problem is, those 'good' shocks are very expensive... you find them on higher end motorcycles, and as aftermarket shocks for offroading (king, fox, etc), and racing. they typically have external reservoirs and offer adjustable low speed, high speed damping on both compression and rebound. tuning them is an art form.
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Old 11-05-2018, 06:02 AM   #20
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Originally Posted by Donna D. View Post
Did I miss what trailer you're towing? Hummm, if you post that, perhaps someone towing a matched set would post and be more helpful. Because right now it appears we're throwing noodles at the wall and hoping something sticks...
He's been coy but at 5000 lbs seems it has to be a Bigfoot.
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