Bouncy Rear End

Bouncy Rear End

Postby Manny ManVan [OP] » May 10th 2020, 4:07am

Since installing 2-3 inch JOR lift kit rear end is very bouncy and sway left to right on the highway while cornering. Replaced shocks at same as the lift. What is causing this? I figure replacing the leaf spring and adding some stops should help???
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Re: Bouncy Rear End

Postby Wiley » May 10th 2020, 2:55pm

What shocks did you go with, were they really cheap? How about the leaf springs, did you swap with stock or make a change? A 2-3 in lift should not change much, is the van empty or full when bothering you? I believe there is an option to add a rear sway bar, but again 2-3 is not much.
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Re: Bouncy Rear End

Postby tungtide » May 10th 2020, 3:13pm

Better shocks for bounce. I used the Lumpy shock mod and stock size shocks. If you used shackle extension for lift, I believe that will ad to sway. Anti sway bar will help. The stops/bumpers should not be coming into play here unless heavy load. Best luck!
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Re: Bouncy Rear End

Postby Mmusicman » May 10th 2020, 3:28pm

Suspension is actually pretty simple:

* Shocks dampen bounce
* Sway bars control sway
* Lift (shackle, block, or body) has virtually no affect on ride.
(vehicle body is merely lifted higher up above stock suspension)
* Springs are springs.. (with different rates/load capacities)
Wrong springs can give weak.. or stiff ride.. but bounce is strictly controlled by shocks.

Manny ManVan wrote:Since installing 2-3 inch JOR lift kit rear end is very bouncy..

A bouncy rear end sounds like weak/bad shocks... not lift.
Test: bounce rear.. if it bounces more than once shocks are bad.
Firm good quality shocks won't bounce at all.. they will simply rebound to ride position.

As always.. I personally highly recommend KYB Monotubes. Great bang for the buck!
Nitrogen gas shocks have amazing control on dampening bounce in varying conditions.

...and sway left to right on the highway while cornering...

Higher lift can lead "some" increased sway and side-wind loading.
Not only more surface area for cross-winds, but higher center of gravity too.
Good sway bar is recommended.

Sway problems are often typically from poor tires or alignment too.
Passenger tires have WAY TOO MUCH flex in their sidewalls for vans.
LT tires (with firm side-walls and higher pressure) is STRONGLY recommended as well!
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Re: Bouncy Rear End

Postby markmitch » May 10th 2020, 5:20pm

Or you could find some overweight people to ride in the back, just saying! LOL
hope you figure it out.
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Re: Bouncy Rear End

Postby Astro Pop » May 10th 2020, 7:28pm

Bounce is bad/wrong shocks, plain and simple. The JOR lift is longer shackles which needs longer shocks in the back. Using the original type shocks puts the shocks outside their normal range of movement. You'll need replacement shocks that are 2-3" longer. I went to 4 wheel drive to get new shocks and they looked them up for me. I forgot which part # I ended up with but they work great. I'm sure someone here has some numbers.....anyone...anyone? The Lumpy mod works great to clear the undercarriage if you're going to do serious 4 wheelin, but you need a good welder and welding skills.
Mmusicman is right. If you have passenger car tires on it....loose them. WAAYYY to mushy for our vans.
Edit: forgot to mention that if you go with the Lumpy mod you can stay with factory shocks.
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Re: Bouncy Rear End

Postby Rinny » May 10th 2020, 10:12pm

My van corners like it is on rails. I went with the 2100lb rear leaf springs made or the van, Journey hangers and shackles (modified them a bit), modified the bottom shock mounts so they are even with the bottom of the axel tubes. The van rides a little stiff when all my fishing gear is not in it but when I am loaded to go it rides well. My front and rear bumpers are quite hefty which helps take out some stiffness in the ride. It does corner really, really, well
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Re: Bouncy Rear End

Postby Mmusicman » May 10th 2020, 11:04pm

ALL springs suffer from the same issue.. they should be matched to the load they are carrying. Empty vans ride firm... loaded vans ride a little smoother. This applies to all vehicles.. particularly heavy duty trucks. There are very different definitions of "bounce".. but it's likely we're talking about slow bouncing up and down, and not a firm bounce over a small bump.

It also depends on the "feel" you are looking for. Some like a firm ride, some like it soft.
GM typically puts the ride somewhere in the middle.
Firm springs are also effective in preventing lean.

Personally, I prefer a firmer solid ride.

All springs bounce (at different rates)... and thus the job of the shock to dampen the rebound.
Shocks may need to be ideally mated to the spring rate.
The heavier the vehicle (or more sever the duty)... the heavier and firmer the shocks.
Weak springs, standard shocks.
Firm springs, firm shocks.
But ALL shocks must dampen rebound. If it bounces more than once, they are bad.

Gas shocks tend to be firm on rebound control, yet internal valving prevents them from being harsh on hard bumps. The pressurized nitrogen gas also prevents "aeration and fade" under severe duty, such as a long bumpy bouncy road.

The right shock is the key to a good successful ride!
So are the right tires.

PS: If your "stock length" shocks (on a lifted vehicle) are extending (reverse bottoming out) to their limit.. you will likely experience a whole new set of problems.
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Re: Bouncy Rear End

Postby Manny ManVan [OP] » May 11th 2020, 9:13am

I used the recommended Rancho RS55150 and RS55147. I think my leafs are just packed out?

I’m going to redo my lift once I’ve rebuilt my front end and use the S10 22687 springs. I want the extra lift and I want it to ride like a truck. I have a pop up rooftop tent as well as bike rack on the back. Thanks for all the input. Pretty much should have just read a few threads before posting.

Sounds like the new shocks I installed when I did the lift are not the right ones??

I’m running Goodyear Duratracs so it’s not a tire issue. I’m thinking it’s the shocks for sure.
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Re: Bouncy Rear End

Postby AstroWill » May 11th 2020, 7:30pm

Definitely sounds like shocks.

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Re: Bouncy Rear End

Postby Manny ManVan [OP] » May 12th 2020, 1:29am

Thanks for all the input guys! I’m will definitely paying much more attention to this site in the coming months. Major upgrades soon to come. Super excited.
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