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Major stability issue at highway speeds

AZCooWhip

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Sounds to me like a suspension issue that is showing up due to the added weight of the wheels. Improving the suspension should do the trick.
This.

37”s at 13.5 .....3” lift here W/ Falcon SP2s.... Tires run at 30lbs. JT drives like a dream and at 20+mpg.
 

Wbrook24

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Ya somethings loose. Might see some mild side effects without a track bar and controll arms but probably not this dramatic. Let us know. Im running a 1.5 leveling kit with 37 bfg ko2s load c untill I put my lift on and it has been solid.
 

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I have a 2021 JT Sport with 37”x12.5” ko2s on 17” rims



When I’m on the highway and hit a bump in the road the entire cab starts rocking back and forth so hard that the traction control turns on and I have to slam on the breaks to get it to calm down. It feels like the truck is going to flip over.

I have the 2.5” skyjacker spacer kit installed on it, but it only started doing this after I put 37s on. It drove fine with 33s on the same rims and lift.

Any idea what else could cause this excessive body sway/cab shaking?
i didnt take the time to read the replies, because the vast majority of people here have no fucking clue what they are doing. but here is your answer

37’s wander more. They just do. And they stress the steering components. You’ll get a ton of people that want to argue with me, but you cant do a budget build and drive 37’s like a stock truck.

if you want 37’s, here is your MINIMUM requirements to have it drive right over the long term. This isn the way I would (or did) build my truck. Its the MINIMUM. And peopel who say less is fine dont have sufficient experience or feel to have an informed opinion.

-adjustable lower control arms. You MUST get caster to 6°. Period.
-upgraded drag link
-upgraded tie rod
-upgraded steering box or shaft brace
-upgraded ball joints
-end links
-re align the truck to .1 toe in and the afore mentioned caster. Make sure your other angles are in spec.

thats the bare minimum to just get the truck to drive straight and be reliable. It is still far from optimized. The better answer is upgrade the dampers, or better yet the springs and the dampers.

there’s no $250 option to run 37’s. Thats just the way it Is.
 

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CoreyOringderff
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It drove much better after tightening the loose sway bar end link. Wasn’t 100% but it did good going 75 until I got a low spot on the road. Hoping that was my main problem but I do plan on at least getting a new lift with an adjustable track bar and lower control arm soon.
 
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Unfortunately that didn't fix my problem after taking it on a second test ride at 70mph. I can't feel any of the swaying in the steering wheel, it points straight with no vibration at all while the whole cab is wobbling and traction control starting.

I know the caster off more than what is optimal, but I think I should be able to feel that in the steering wheel. My next theory is that my loose sway bar damaged my shocks and they aren't dampening the springs appropriately.
 
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Did another look under my Jeep and found that the rear track bar is missing the bolt to the frame. I think it is a M14, but I'm not sure about the length. Going to throw a 1/2" Grade 8 bolt in there to hold it together until I can get the OEM bolt and nut.
 

JAVIERGONZO

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i didnt take the time to read the replies, because the vast majority of people here have no fucking clue what they are doing. but here is your answer

37’s wander more. They just do. And they stress the steering components. You’ll get a ton of people that want to argue with me, but you cant do a budget build and drive 37’s like a stock truck.

if you want 37’s, here is your MINIMUM requirements to have it drive right over the long term. This isn the way I would (or did) build my truck. Its the MINIMUM. And peopel who say less is fine dont have sufficient experience or feel to have an informed opinion.

-adjustable lower control arms. You MUST get caster to 6°. Period.
-upgraded drag link
-upgraded tie rod
-upgraded steering box or shaft brace
-upgraded ball joints
-end links
-re align the truck to .1 toe in and the afore mentioned caster. Make sure your other angles are in spec.

thats the bare minimum to just get the truck to drive straight and be reliable. It is still far from optimized. The better answer is upgrade the dampers, or better yet the springs and the dampers.

there’s no $250 option to run 37’s. Thats just the way it Is.
Well if you spent less time being aggressive and did read you'd see that most of us agreed he needed suspension support for the 37s.
 

adlambert11

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I used to get that on my '95 Cherokee, it ended up being the steering stabilizer.
 

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I used to get that on my '95 Cherokee, it ended up being the steering stabilizer.
No, it didn't. It may have made things feel better but it "fixed" nothing. You still had major issues with your steering/suspension.
Experts have talked about this until they are blue in the face and yet.......

Quotes from engineers and those who specialize in steering and suspension don't seem to matter, but here are some again:
-----------------------------
(Quote from Norm Layton, owner/crew chief 4540 Motorsports):
A steering damper is not a fix, it's a band-aid used to mask issues with either worn components or poor design. Dampers did not start appearing on stock vehicles until the late 70s, mostly associated with the trend to larger (wider thus heavier) tires on older designs.

On a properly designed and well maintained system, a damper's purpose is to mitigate the effects of bump steer and the sudden encounter of unexpected objects, such as hitting a rock in a trail at 50 miles per hour. On an improperly designed and/or poorly maintained system, a damper is used as a crutch to mask issues with suspension and tire errors.

Jeeps and other vehicles experienced shimmy way before the 1960s, and before the advent of lifts and larger tires. Worn components are just as much at fault as jury-rigged suspensions.
----------------------------

Suspension engineer Bob Sheaves wrote:
"Death wobble" first showed up in vehicles in the 1960s with early aftermarket lift kits, primarily on Jeep CJs and Land Rover S1s. The steering linkage was a single rod from the pitman arm down to the tie rod, attached at both ends with a ball joint (tierod end) called the draglink; and a single rod from the left to right knuckle that was the tie rod.

Jeep Gladiator Major stability issue at highway speeds death-wobble


-----------------------------
And this is going to piss off some of the hard-core guys:
This is why I keep harping on SCRUB RADIUS (Scrub Angle) and if you have TALLER tires, wider wheels, or if you decide you like the looks of big tires sticking out - you are literally asking for death wobble. May not happen but the suspension is designed specific ways by engineers - making such changes negates the engineering.
You totally change the ANGLES of the the linkage - suddenly things aren't being compressed, they are being "bent" or "bowed" due to the downward angle. They flex. They'll resist end-to-end compression but can't resist bowing or flexing. The bigger the lift and the bigger the tires, the more prone to death wobble.

The stuff above is from engineers and experts - not the arm-chair type from all over fakebook and other places.

So taller tires, wider wheels, setting the center of the tire outward - doing any or all of that without doing the math............
 

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Did another look under my Jeep and found that the rear track bar is missing the bolt to the frame. I think it is a M14, but I'm not sure about the length. Going to throw a 1/2" Grade 8 bolt in there to hold it together until I can get the OEM bolt and nut.
Dude, I would get it home and retorque all suspension bolts to spec and put a witness mark on them with a paint pen for easy future monitoring. I don't know of you put your lift on or a shop, but I would not go back to the shop if that is the case. You can use the mopar lift instructions for the torque specs and wrench/socket sizes. The lower control arms will be the most difficult (195 ft. lb, iirc).

You should do this for peace of mind, but the track bar bolt missing takes the cake.
p.s. x2 on longer lowers t a minimum. Your poor geometry is simply amplified the bigger tire you go.

good luck bro

eric
 
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I had a local shop put it on that was recommended by a friend who said the shop owner worked on jeeps. I decided I wouldn't go back to them last week when they told me I had to replace my upper control arms if I wanted to upgrade ball joints and that I couldn't supply my own parts.

Now that its all bolted together it rides great. I have no complaints from the lift creating bad geometry or anything. I'll be upgrading to a more complete kit in the future but right now the lift/stock suspension is handling the 37s great.
 
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Jeep Gladiator Major stability issue at highway speeds 9988D637-CA8D-4EBB-80A9-126C7FFBD123
Here is a picture of my truck since I’m so hyped that it can be driven again
 

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I had a local shop put it on that was recommended by a friend who said the shop owner worked on jeeps. I decided I wouldn't go back to them last week when they told me I had to replace my upper control arms if I wanted to upgrade ball joints and that I couldn't supply my own parts.

Now that its all bolted together it rides great. I have no complaints from the lift creating bad geometry or anything. I'll be upgrading to a more complete kit in the future but right now the lift/stock suspension is handling the 37s great.
Sounds to me like the shop didn't properly torque parts after the lift - and installing such a lift without at least discussing the lower control arms to get caster back in line - seems a bit like they missed the boat. Working on Jeeps and knowing what you are doing are too often two different things.
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