Violent vibration from front end only on full throttle. HELP

[Mechx269]

I know I'm new to the forms but I have used the search function to see if I could find a resolution to my issue. I couldn't find anything. I have a 04' 4x4 trailblazer with a MarkMC 3" suspension lift, a MarkMC 3" body lift, and 4.10's installed on both the front and rear on 35" tires with MarkMC wheel spacers. I love the way the truck looks and I want to solve the issue so I could drive it more often. The issue I'm having is that when I go full throttle the front end of the truck vibrates violently, but during normal driving or about half throttle I don't have any vibrations. The only thing I could think that is happening is that when the weight transfer to the rear happens the front axles start to bind up due to having an aggressive angle. A couple of solutions that I came up with is removing the front 3" suspension lift and replacing it with a 2-2.5" suspension lift OR replacing the rear springs with the z71 springs to give it more of a raked stance to help reduce the weight transfer. Any help would be much appreciated! I want to finally solve this issue and get back on the road! Thanks!

[Rickalicka18]

Damnnn your rig looks awesome man. Have you check u joints? Having the same problem in the rear on mine.

[Mechx269]

Thanks, but its been the biggest headache since day one lol, but I know I'm at the final steps on having this project completed! I have checked the u joints, but none of them have any play and when I go full throttle in reverse I don't get the vibration which is why I believe I have a aggressive angle with the front CV joints when the weight transfers to the rear during forward full throttle.

[Rickalicka18]

Does it do it get worst in 4wd?

[Mechx269]

Nope, it does the same thing in all forward drive modes. Reverse full throttle doesn't produce a vibration, and I think its because the weight is shifting to the front.

[Anthony Hernandez]

Meh, add a bumper an skids bro.. Might help the cv angle...

[Mechx269]

I would but my wife already said that I spent way too much on this truck to get a bumper and skids lol.

[Jrgunn5150]

Weird, mine does the same thing. I thought it was my upper balljoints

[DirtyBacon04]

Simple way to test. Jack up the front of the truck so the wheels are at full droop, turn it by hand and see if the CVs are binding.

[v7guy]

I would wager the CVs are probably fine, even with 89s and the 3" lift I wasn't getting any bind in the CV. I would look more at the balljoints, bushings, and tie rods up front. I think the first spot I would look is the upper A arm bushings, I've never seen one of these things that had them in good shape.

[markmc]

That truck looks familiar...
Does it vibrate with the factory tires and wheels?
Did you get a front end alignment ?
Check the motor and trans mounts ?

[Jrgunn5150]

I would wager the CVs are probably fine, even with 89s and the 3" lift I wasn't getting any bind in the CV. I would look more at the balljoints, bushings, and tie rods up front. I think the first spot I would look is the upper A arm bushings, I've never seen one of these things that had them in good shape.

Huh, this is pretty solid advice, since mine definitely started after the lift. Since it only does it on very hard acceleration, I haven't been too bothered by it, but I do have a new set of control arms here to go on someday.

[Mirage]

Thanks, but its been the biggest headache since day one lol, but I know I'm at the final steps on having this project completed! I have checked the u joints, but none of them have any play and when I go full throttle in reverse I don't get the vibration which is why I believe I have a aggressive angle with the front CV joints when the weight transfers to the rear during forward full throttle.

You checked the u joints for play but what you need to do is remove the shaft and check for binding. Your truck had the same driveline angle since new and it has now changed with the lift. Your u joints are not oriented in the driveshaft the same as they were at stock ride height.
Your front axle does not have any bearing on this unless you are in 4wd.
I'm sure you have a seizing rear u joint.


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[Rickalicka18]

Mechx269, does this only happen to you when you intially start accelerating from stop? Mine does shake violently on hard acceleration too but its at its worse when I accelerate from stop. While cruises its pretty smooth. Might be the exact same problem I have just worse... I'll be going into see my mechanic soon because he wants to do a check up on my lift kit and suspension and I'll see if he can diagnose the problem then. Pretty sure its just a u joint. But ya neva know. That is if you haven't figured it out the problem by then.

[Mechx269]

sorry it took so long to respond. lol its the same truck markmc. You did a great job by the way, I was blown away once I got back from Korea. I did replace the control arm and ball joint on the right side, but not on the left. The car was aligned when the lift was installed, but i did notice today while driving that the steering wheel is pointed like 20 degrees to the right while going strait. I did look at the upper A arm bushings like v7guy had mentioned. The left side control arm has a little wear and the ball joint has a torn boot but doesn't have play. I think I'm going to replace the left upper control arm and ball joint and at the same time do the UCA flip and switch, then get another alignment. I didn't realize how angled the upper ball joint is after getting the lift done until today! Rickalicka18, the vibration is worse from a dead stop, but if I floor it at about 40 mph, I get the same vibration once I feel the truck weight shift to the rear. If replacing the control arm doesn't fix it, I'll remove the drive shaft and inspect the U joints much better. Thank you all for all the input!

[Craig]

Had a similar issue. When parked put pressure on your brake and ease on the gas as if you were doing a brake stand. If you have someone look at the engine they will see the engine lift up on one side thus showing you which motor mount needs to be replaced.

[hilljb]

When I lifted my TB, I got an absolutely horrible shake under acceleration in the front end. I hadn't experienced it at all before the lift and subsequent alignment. Mine turned out to be the CV axles.

I'm not sure that you're necessarily going to experience bind-up in a bad CV axle without being able to put a a good amount of torque on it. It's the torque (rotational acceleration) that really makes them wobble about. Hitting the gas from a stop or from low speed made them bounce around like crazy, while hitting the gas at higher speeds caused less overall acceleration and less of a wobble. It was also worse in 4WD, but that was incredibly hard to determine simply because you generally aren't in a situation to punch the gas and accelerate with 4WD engaged. I never did try to diagnose it in reverse.

Keep in mind: Never engage 4WD on dry pavement. It can cause this very problem, which is more noticeable when the truck is lifted. (Mine were probably bad before I lifted the truck, but I never noticed it.) If you're driving a lot with 4WD on dry surfaces (pavement, slick rock, etc.) you may want to plan on replacing the CV axles every so often. They're not too challenging to replace, and you could always use your old ones as spares if they aren't blown completely.

I also agree with Craig that motor mounts could cause that sort of vibration. But, if you're coming off a new lift and seeing this, it's probably the CV axles (or, at least one of them).