Jeep JK - Vibration issue (not death wobble)

[exilei]

Hi All

I have a JK 2011 3.8 Auto which has developed a vibration which occurs at @50-55km/hr then again at @80-85km/hr. It feels like it is more from the rear than the front. A few things I've looked at so far: -

1/ Ball joints replaced not long ago
2/ Rear tail shaft cv's: they had a bit of play so new ones on order. (I removed rear tail shaft and test drove car in 4wd Hi range so basically front wheel drive. Hard to tell if cv's were the issue as car handled so differently with that set up.
3/ Rotated wheels front to back: Vibration still seems to be from rear so don't think its balancing.
4/ I've found one of the rear spring isolators is split between the spring and body. Could this cause vibrations at different speeds?

Any suggestions would be appreciated.

[Hayesio]

Hi exilei. So far, you seem to have good systematic approach. Sometimes it's so hard to find what's causing these problems and you drive around for months or even years putting up with it; i know i have.
Can I suggest the following:
Did you change anything just prior to this developing? tyres, bearings, balancing etc?
Were you off-roading, etc before problem presented? Have you inadvertently damaged the drive shafts or seriously damaged tyres?
Maybe you can remove the front drive shaft, drive car and see if problem is still there?
Have you got a double cardan joint shaft in the front that has not been lubricated? (companies like JL Reel don't think to bother with center yoke grease points so they inevitability self destruct).
I know you have new ball joints, you should inspect just the same - early failure is common including leading bands, inc.Synergy and alike.
Inspect engine and transmission mounts.
Use clutch/neutral to eliminate transmission/clutch/flywheel as the cause.

[exilei]

Thanks for the reply.

I hadn't thought of removing the front shaft and will give that a test.
Nothing had been changed prior to the vibration, nor had any heavy offroading been done.

The vibration was barely noticeable at first but has continued to worsen which suggests something wearing rather than a sudden failure.

I'll re check ball joints as well.

I haven't checked engine or gear box mounts.

I don't mind spending money to fix things but it's disappointing throwing money at something and the problem still remains.

Any thoughts on the rear spring isolators?

[OzRick25]

I have had intermitent vibration/noise from:
The double cardan
Suspension bushings
wheel bearings

I'd check your rear sway bar connections. However noting you think it's from the rear, your 3" lift, and your rear dive shaft has movement; then the rear diff pinion bearing and wheel bearings would be the first place I'd look

[exilei]

Thanks Rick,

I hadn't thought about the wheel bearings as I thought if they failed they would rumble constantly rather than intermittent vibrations. I'll check them out though.

When I'm changing the cv's I'll inspect the diff pinion.

I've checked the swaybars and everything looks as it should.

[OzRick25]

Originally Posted by exilei

Thanks Rick,

I hadn't thought about the wheel bearings as I thought if they failed they would rumble constantly rather than intermittent vibrations. I'll check them out though.

When I'm changing the cv's I'll inspect the diff pinion.

I've checked the swaybars and everything looks as it should.

When they are properly cooked they rumble constantly, when it started out though it was intermittent. I think when its just starting it may be one or a few rollers that are jamming up slightly so when those rollers get to TDC they take weight and cause the vibration but at bdc the good rollers hide the issue, no bearing expert but mine started out intermittent and after a few thousand more kms they were really noticible all the time. My front bearings went first though.

I've also had a more constant vibration from loose bash plate bolts, it was more annoying at lower rpm

[Banshee]

I had constant vibration from mine. It turned out to be a couple of things...

Tyres that had bumps on them, so they weren't round, and 2 slightly warped rims. Both spotted while they were being balanced by looking at the surface of the tyre as it was spun & the inside edge of the rim.

New tyres & swapped rims with good ones & most of that has now gone.

BUT, you would also notice that as slight vibration in the steering wheel if you had one of them on the front.

If it seems to be from the back, have you had a look at the tailshaft for dents? Also there are usually balance weights on them somewhere. Does it look like there are marks when they might have come off recently?