Vibrating Jeep over 45 mph

PhillyJake

TJ Enthusiast
Original poster
Joined
Sep 22, 2020
Messages
106
Location
Philadelphia
Hi All - looking for a place to start as I diagnose a new vibration ('04 Rubicon TJ; 4.0 manual) - thanks ahead of time for taking the time to read through this.

I've owned her about a year and in that time I've replaced the rotors, pads, calipers; shocks; flushed the transmission fluid; cleaned the throttle body; and I have 4 new NGK O2 sensors coming this week (CEL been on for a minute throwing P0161 & P0158, both related to B2S2 sensor, but may as well get 'em all).

She's my daily, but I don't commute b/c of COVID, so usually don't go over 40. Took a highway drive this weekend (approx. 100 miles/2 hrs.) and now, from 45-50 mph, the Jeep starts to vibrate consistently until I drop below 40 again - regardless of gear, acceleration or deceleration, incline or decline, driving straight or on a curve, cold or hot engine. I can feel it in the steering wheel, but this doesn't feel like an alignment issue or death wobble...more like the whole rig is resonating with whatever's causing the problem. I can feel it really strong in the gear shift.

No new noises, no smells, and apart from this new vibration, she's driving like normal and doesn't pull under hard braking. I've done a bit of work over the past 3 weeks, and maybe that's caused the problem: replaced back passenger bar pin eliminator (driver side fine, no work); tightened the hand brake (at the wheels and under the car); bought and installed a hardtop (I thought maybe the new weight or aerodynamics might be a thing?). Took off the back tires to do the shock and brake work and tightened the lugs on the spacers and the wheels to 100 ft/lbs (both came with the jeep when I purchased) - I did struggle with the lugs on the wheels, seems like there may be some cross threading, so maybe my rear wheels are wonky?

Based on my searches, I'm going to check the following, though not sure how to prioritize, so open to any guidance all you wonderful people can offer:
  • U joints
  • Play in the drive shaft
  • Wheels/tires out of round
  • Could it be a transmission mount? I could replace that while getting at the sensors - or another trans issue? pretty sure my synchros are on their way out, and the clutch makes noise when not engaged, but that's old news
Again, thanks in advance for reading and any thoughts or advice you can offer! As a reward to those who made it this far, a pic for your efforts:
Jeep.webp
 
Speed specific is usually tires
 
Have you had it lifted since the last time you hit highway speeds? The steeper angle of the driveshaft will cause vibrations.
 
Have you had it lifted since the last time you hit highway speeds? The steeper angle of the driveshaft will cause vibrations.
good question, but she came lifted and I haven't done anything to affect the ride height (I think), unless fixing the rear shock somehow mucked with the driveshaft.
Balance the tires first.
nice - thanks to you and JMT for pointing me to the right first move - i'll get that taken care of this, get the tires rotated and balanced.
 
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Reactions: TheBoogieman
good question, but she came lifted and I haven't done anything to affect the ride height (I think), unless fixing the rear shock somehow mucked with the driveshaft.

nice - thanks to you and JMT for pointing me to the right first move - i'll get that taken care of this, get the tires rotated and balanced.

Hi, I know this post is like 2+ years old now but I wanted to see if you ever figured out what was causing this issue, whether it was the tires or something else. I bought an automatic 05 Rubicon a few months ago and since the day I test drove it I have been having a pretty identical problem to what you have described with vibrations over 45 mph and have yet to figure out what the cause is. When I bought it the dealership assured me that it had been inspected in-house and their guys drove it and found absolutely nothing wrong with it whatsoever, but there were two different sets of tires on the front and back of the jeep, same size but different weights, so I figured the issue was probably with the tires, which needed replaced anyways. However after getting all new tires, there was absolutely no change. After looking into it a bit more, I was thinking it was very likely to be a bad u-joint, something with the driveshaft, or even a bad engine or transmission mount but still didn't know anything for sure so I just took it to a mechanic yesterday to finally figure out what the real culprit was. I just got it back today and the mechanic said he found absolutely nothing wrong with it, no play in any u-joints or anything else he could see without starting to seriously take things apart. Because of this, he said although the vibration is there, he isn't really worried about it and wouldn't worry about it unless it gets worse but I feel like, especially if I'm driving for extended periods of time at highways speeds, it has to be harmful to the longevity of the jeep so I don't really want to just wait until it gets significantly worse or something breaks and really want to try and figure out what is going on. Anyways, really hoped maybe you would have a possible answer or any insight with how your issue was resolved, thanks! :)