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Unstable over bumps


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31 minutes ago, derek01f said:

I've noticed my truck is very unstable when going over bumps on the road, doesn't really matter my speed, but the truck becomes very "loose".  Anybody else notice this?

Do you have Z71 suspension package with the Rancho shocks?

What trim package if so? Trail Boss or other?

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Well IMHO as I have stated before in the 2014-2018 truck section, it is the Rancho shocks.

Trail Boss and AT4 are equipped with the Monotube version which is better than the twin tube design on your truck.

Twin Tube Ranchos are not dampened very well and are lackluster on roads where there are railroad crossings, pot holes, washboard sections etc.

They are also spongy and the rebound is off when off roading.

 

Edited by Sierra Dan
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47 minutes ago, derek01f said:

I've noticed my truck is very unstable when going over bumps on the road, doesn't really matter my speed, but the truck becomes very "loose".  Anybody else notice this?

Please tell us about your tire size, air pressure, etc.

Lower profile tires and over-inflation will make the ride worse no matter what shocks you have. Trucks do ride rougher when completely unloaded.

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Fresh from dealer when I brought it home the truck had 41psi in each tire, I took that down to recommended level, right around 35

 

I also put new tires on the truck and it does the same, these tires are Cooper Discoverer AT3 XLT - 275/70/18

updated-pics.jpg

Edited by derek01f
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It's been discussed here. I got flamed when I mentioned that!

That's why I have ten on my ignore list. The back end fishtailed so badly I nearly ran over a guy on the side of the road. It was a straight road with dried dirt on top from a recent storm. I was so surprised it fishtailed when I wasn't hitting the gas or braking on a straight road.

 

Solution: the tires were inflated at 45 psi or 44, well above the recommended 35. I have no idea why it came like that and letting air out helped a bit. The next two times, it fishtailed but wasn't as bad as the first one. I was so mad, I nearly ran over a pedestrian. Like you, I have an RST 4x4 so I know exactly where you're coming from.

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I was doing around 80km/h and hit a washboard area in the road.  The truck began to yaw and was nearly sideways before I was able to recover it.  Stabilitrak never kicked on. Road was dry.   Bounce was so bad the tonneau cover actually detached and landed on the road.  I have the max trailering package so the suspension is tight to begin with.  Scared the hell out of me for sure.  Bumps, potholes and train track crossings are rough but not to the point of losing control like the washboard area did.  Never experienced anything like it in my past GM pickup trucks.

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It's not just the Z71 and max tow packages.  I have the RST non-Z71 and like previous pick-ups it too fishtails on washboard roads.  Unfortunately this is the worst I've ever seen and I buy a new chevy every three to four years.

 

Like others have said, adding weight to the back will help but it's not going to go away completely.  Bilstien 5100 shocks also help but there is no real solution.  Heavy springs designed for the payload/ towing wars combined with a now lighter weight back end means more fishtailing.

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Welcome to the Z71 T1 walking rear end club. 
 
You're not alone, fellow Rancho victim. Lol


Well I’m kinda glad to see it’s more than one person. Crappy problem to have, I noticed it early on and no matter what I have done, wheels/tires or different air pressures it all reacted the same way.

Shocks are on top of the mod list right now. I’m waiting for fox to release a 2.0 coil over good for two inches of lift so I can do something like a trail boss setup
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8 minutes ago, Bluerado23 said:

 


Well I’m kinda glad to see it’s more than one person. Crappy problem to have, I noticed it early on and no matter what I have done, wheels/tires or different air pressures it all reacted the same way.

Shocks are on top of the mod list right now. I’m waiting for fox to release a 2.0 coil over good for two inches of lift so I can do something like a trail boss setup

 

Fox coil overs will most certainly help smooth things out. 

 

Mostly, this is just the result of trucks getting lighter, but able to carry more payload. Stiff rear ends when empty. 

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3 hours ago, Cooper 114 said:

I was doing around 80km/h and hit a washboard area in the road.  The truck began to yaw and was nearly sideways before I was able to recover it.  Stabilitrak never kicked on. Road was dry.   Bounce was so bad the tonneau cover actually detached and landed on the road.  I have the max trailering package so the suspension is tight to begin with.  Scared the hell out of me for sure.  Bumps, potholes and train track crossings are rough but not to the point of losing control like the washboard area did.  Never experienced anything like it in my past GM pickup trucks.

 

Exactly the same situation I was in. That is a liability issue, I was more angry over the fact I could have killed the guy walking on the side of the road. GM fanboys got all over me on this, questioning my experience, etc. "My Ford did the same" I've driven 4x4's and none were this bad. I was going about 70 km/h, maybe 80 km/h when it happened. That is why my next car isn't going to be a Chevrolet unless they address this.

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