Broke down and bought a new 2008 Sequoia with the 5.7L engine. Nice vehicle. Couldn't pass up the great price. Anyway, love the vehicle and the power, but have noticed an annoying bounce in the vehicle. It seems that the back end bounces up and down about 1/2" or so a few times per second on the highway. Mostly disappears below 30mph. More noticeable on concrete roads, but still there on asphalt. Same hitch height, same trailer, same loading as the last TV. Only difference I can see is an independent rear suspension vs. solid axle. Both had coil springs and shocks. Adj. WD bars and it made no difference other than the pitch of the TV. Would stiffer shocks or air bags in the coil springs help? Something else? Is that the nature of the independent rear suspension?
It is probably more related to the length of the vehicle and your trailer. It seems like some highways have minor bumps that cause some to bounce. Tongue weight may be the answer. Since you have adjusted the torsion bars they should not be the problem, unless they are too light. Good luck
Did you see that clip on youtube comparing the Toyota to the Ford on washboard roads? OK, what you are likely experiencing is bounce caused by the soft suspension of the Sequoia. Possibly tires are a contributing factor too. Get some real weights and lets see what you got then. Also I noticed you stated same hitch height? Unless it was an exact same vehicle that may be contributing to the problem.
Possibly stiffer shock absorbers would help? And... are the tires in good shape? I know it is new, but it is not unheard of for new tires to be defective, there may be something wrong with the tires.
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2008 F-250 CrewCab 5.4L,
2004 21' Forest River Surveyor
I'd put on some good mono-tube shocks like Bilstein. Each year SUV suspensions get softer, which makes a nicer ride, but is not ideal for controlling the oscillations that can happen with some loads.
Airbags alone could actually make the bounce worse, since they don not provide any dampening.
Bryan
2000 Ford E350 DRW Wagon (14-pass all captains chairs)
V10 w/ Banks PowerPack, Diablo Predator, 4.56 LS, 230,000+ miles
Had: Weekend Warrior 41' FSW (still looking for its replacement)
Different from vehicle to vehicle, road to road and even speed.
All things will vibrate at a 'natural' frequency. Dwell at that and the
amplitude will increase, as every input at that freq is additive.
Change something in the vibration food chain and it will reduce or
knock it down far enough to not notice.
Tires are the biggest shock absorber on any vehicle. The class (P, LT
or commercial) makes a difference. As does the load rating, as does
the size, as does the profile (aspect ratio) and of course PSI.
Just changing the speed can reduce it enough. Speed as in how often it
encounters the joint strips. That changes the input frequency, so it
might move it away far enough from the natural frequency.
Changing pressure in the tires also a good way to test.
Changing the WD setup also might help. Tightening the tension on
the WD bars, higher rate bars, etc. Hope your setup has the trailer
and tow vehicle level and that the trailer pointing at it's highest,
level and better if pointed slightly down when the WD bars are fully
tensioned.
Then the expensive stuff. Change the shocks, change the suspension
bushings, change the springs, etc, etc. all affect the natural freq
(harmonics).
Why you'll get many, many differing inputs/advice that all worked
for 'them' and 'their vehicle'.
You'll just have to play around with it till you knock it down enough.
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...
Running 40 psi in the TV tires. Trailer is around #5500 loaded. 650# tongue weight before drawing up the WD bars, then only #400 on the TV, 170 front, 230 rear. Truck and Trailer are both level. Receiver height is the same on both vehicles. When hooked up, jumping on the tongue didn't flex the sidewall of the TV tires much, but the truck sure bounced up and down, that is why I thought the springs/shocks/independent suspension might be the problem. I'll have to check the wheelbase/rear wheel to trailer wheel distances to see if they are similar. There is a 3+" longer wheelbase on the new truck than my old one.
Just sounds like "harmonics" of the TV's wheel base versus the length or distance of the seams in the concrete highway.
Our freeways here in San Jose, Ca. are mostly concrete, and they have seams or expansion joints in the slab. When I drive on them with my 160"+ wheel base Dodge Ram, it will develop a real bumpy harmonic in the suspension at certain speeds. For my truck and our nearest freeway, it is around 55-60 mph.. If I slow below those speeds or go above those speeds, it smooths out.
The poster mentioned that this happens at a certain speed and on concrete.........I think it's just a harmonics-thing. It isn't that much different than the way the Tacoma Narrows bridge collapsted back in the 1940's. Everything that moves or is mechanical can be affected by harmonics. I think the Sequoia's suspension/wheelbase length hits a certain harmonics based on speed and distance of expansion joints or bumps/ripples in the highway.
Anyone remember the old military term when marching foot troops over a suspension bridge......I can't, but the troops were to not do "left/right" steps in unison, or it could start the bridge swaying dangerously, cause it set up a harmonic wave or sway. The troops were to just stagger their steps or not step left-right in unison, therefore the bridge wasn't getting a left-right pulse from hundreds of troops on a small suspension-type bridge.
Regards, Eightballsidepocket
2005 Dodge Ram 2500 SLT 4x2 Quad Cab, Cummins, 48RE Tranny, Lg Bed, Line-X Spray-on Bed Liner.
06 T25BS Komfort Trailblazer TT
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