Intermittent rear end shake

jckj95 · Jun 5, 2019

hey everyone I’m new here and have owned my KJ since January.
I’ve replaced almost everything on it, front end rear end, the works. It’s throwing me for a loop here lately. At highway speeds (65-75mph) my rear end will get an awful shake and go away, then shortly after it will start again. I’ve checked the driveline and all the u joints seem intact I threw some grease their way while I was at it. Everything is tight that I could see. I have a pinion seal out but that’s about it.
Any pointers in which direction to go would be appreciated.

tommudd · Jun 5, 2019

jckj95 said:
hey everyone I’m new here and have owned my KJ since January.
I’ve replaced almost everything on it, front end rear end, the works. It’s throwing me for a loop here lately. At highway speeds (65-75mph) my rear end will get an awful shake and go away, then shortly after it will start again. I’ve checked the driveline and all the u joints seem intact I threw some grease their way while I was at it. Everything is tight that I could see. I have a pinion seal out but that’s about it.
Any pointers in which direction to go would be appreciated.

Are you sure on the u-joints, they can feel tight but be rusted almost completely together
Also is it just a shake, if so what speed ?

jckj95 · Jun 5, 2019

tommudd said:
Are you sure on the u-joints, they can feel tight but be rusted almost completely together
Also is it just a shake, if so what speed ?

I plan on double checking them tonight. I’d call it a “aggressive” vibration, happens at highway speeds typically 65-75 mph

ltd02 · Jun 5, 2019

I'm assuming you changed the rear shocks at some point in your refurbishment. Maybe you got a bad one? Maybe you can get someone to follow you at speed and see if anything is bouncing when it shouldn't.

LibertyTC · Jun 5, 2019

65-75 mph is also where a bad tire balance can create the vibrations.
Have all 4 tires checked with a shop that has a DIGITAL tire balancing machine.

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In my case the rim was a bit out of round & was supposedly balanced properly by another shop...eek !
Also when you remove the driveshaft it better be marked & put back together correctly.
If not..you are best to have a driveline shop check it over, & have the driveshaft checked on a balancing machine.

jckj95 · Jun 5, 2019

ltd02 said:
I'm assuming you changed the rear shocks at some point in your refurbishment. Maybe you got a bad one? Maybe you can get someone to follow you at speed and see if anything is bouncing when it shouldn't.

Well I was at work tonight and the vibration showed itself, rear u joint. Driveshaft went Heaven bound.

duderz7 · Jun 6, 2019

jckj95 said:
Well I was at work tonight and the vibration showed itself, rear u joint. Driveshaft went Heaven bound.

Don't toss it, have rebuilt. There are driving shops out there in the world.

tommudd · Jun 6, 2019

jckj95 said:
Well I was at work tonight and the vibration showed itself, rear u joint. Driveshaft went Heaven bound.

yep
My 04s ( that I bought new ) went at 55,000 miles, rusted solid
the 03s lasted until 130,000 miles

jckj95 · Jun 21, 2019

Sorry for the late “thank you’s”
But she’s starting her s*it again
Basically the same thing but WORSE
It’s bad, almost constant last night, when pulling a 2 mile 7% uphill grade at 70 I felt it start in the rear then it made its way to the front. I was able to feel it in the steering wheel.
Maybe rear wheel bearings?
I’ve gotta check those tonight when I get to work but I’m at a loss.
Also when I first start moving, and let out the gas (Jeeps got a 5 speed in it) I can hear a very sharp metallic “clang!” I tried to find the source of the noise.
I have a suspicion about the rear upper control arm, as I can move the 2 corners up and down in the bushings

Intermittent rear end shake

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