Bed shimmy at speeds over 65mph, seeking insight, thanks!

[staying_tuned]

Howdy folks, I've got a 21' Willys Diesel which comes equipped with the previous generation Rubicon red shocks (pic below). I'm loving my JT immensely. Just over a month ago I installed the following in rapid succession:

- AEV 2" spacer lift (included relo brackets, end links, shaft spacers, procal etc. Install wen't without a hitch, EVERYTHING tightened to spec. and checked after our first trip out post install.)
- Wheels & Tires (tires are at 34psi and were balanced when mounted)
- Bed rack & RTT

There is a shimmy happening with the bed after 65mph on anything other than very smooth highway. I've had it up to 85-ish and on newer highway, it's a single finger matter and rides nearly as smooth as my wife's Mazda CX-9. That said, the bed starts wiggling back and forth for a few seconds after I go over any sort of bump, dip or ultra shallow pothole. I can feel it in the seat and see the rack wiggling in the rear view mirror. If the stretch of highway is rough, the bed is wiggling the entire time, never really getting a chance to calm itself.

I initially chalked this up to a bad balance and decided I'd take it up with the shop in the coming weeks. After more time with it though, I've been able to identify some patterns. It seems to get worse at the end of extended drives. The worst yet was during the last part of our return trip home after a few hours of straight driving. I then remembered all of the negative feedback over the years on the stock rubi shocks. I opted to keep them for now thinking surely they'd be tolerable.

My current theory is that with the additional of a fixed 300lbs. (rack plus RTT) including any downforce imposed by the tent, these red rubi shocks just aren't up for the task.

I don't want to harass the shop (great shop, well respected) about a balancing issue without entirely ruling out these shocks. Then again I don't want to purchase something unnecessarily. I was quite happy to leverage the shock extension brackets provided in the AEV kit and thought sweet, I'll be able to punt on shocks for at least a year or two.

What do you think and thanks in advance for any insight!

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[sass JT]

More than likely it’s your shocks.

The shocks you have are a mono tube steel body shock. They heat up the longer you go, causing the fluid to foam inside and they give up the ghost. Pretty much standard shocks

An aluminum body shock will help dissipate the heat more, also a reservoir style will give you more fluid to help keep cool too.
The question is how long you can live with the basic shocks and how much you can afford to put into higher quality shocks?

good luck with your decision.

 

[jeepstertim]

After a torque re-check and perhaps try varying the tyre pressure to see if any difference, I'd look to shocks next as well. They're not expensive and as you're not asking anything unreasonable of the platform you shouldn't need anything particularly expensive. Could it be with the spacer lift, you have taken the red shocks beyond their optimum operating length/ damping performance?

JTR take offs might be an economical place to start?

-having reread your post it says over 65, I suspect poor shocks you'd feel at slow speeds too. If your RTT sticks up proud of the roof, it could be aerodynamically induced, try without RTT?

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