Bad vibrations?

I bought a 99 XJ a month ago and ever since I got it there has been a vibration. It usually starts around 55MPH but the weird thing is that sometimes it’s not there and I can go up to 70MPH without noticing it. Sometimes getting off the gas and back on will start it, other times if it’s there and I get off the gas, slow down a bit and then accelerate again it will go away. It’s hard to say where it’s coming from, you feel it all over the Jeep. Although I feel it in the steering wheel, it’s not any sort of a side to side motion that normally accompanies vibes related to the steering.

I’ve had the tires balanced recently.

Any suggestions as to what it could be?

is your rig lifted? If so how much? This information is important when diagnosing problems.

Sorry, it is completely stock. 4L, Auto trans. It has less than 100k miles.

My first guess would be the universal joints.

If it comes and goes I would look at your motor/trans mounts!

RCP Phx said:

If it comes and goes I would look at your motor/trans mounts!

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In the back of my mind I was wondering about that. Sometimes when I come to an abrupt stop there is a little bit of a clunk coming from the transmission area. How easy is it to tell if the mounts are bad?

If you crawl under and can move the transmission back and forth by hand while in neutral. just make sure you choke the wheels first. there should be a little play because of the rubber mount but a lot will be noticeable.

So I was thinking I would just take the mount off to inspect it. How hard is this? I've gone through the FSM and there are no diagrams. The only mention of it is to remove it and then put it back in. If someone could explain to me how it's doen I'd appreciate it.

id check:
Universal joints in the driveshaft
rebalance Driveshaft if needed (Maybe a weight fell off)
perhaps rebalance rims n tires again (again maybe a weight fell off or tire out of round) What is the wear pattern on the tires?
motor n trans mounts as already mentioned.

djblade311 said:

id check:
Universal joints in the driveshaft
rebalance Driveshaft if needed (Maybe a weight fell off)
perhaps rebalance rims n tires again (again maybe a weight fell off or tire out of round) What is the wear pattern on the tires?
motor n trans mounts as already mentioned.

Click to expand...

I was under the impression that driveshaft balance issues are sustained vibrations that get worse with speed. In this case the vibration comes and goes, and is only present between 55 & 65MPH.

The tires are actually snow tires with tons of tread left and no odd wear pattern that I can make out. I'm planning on getting new summer tires next spring.

I'm hoping someone can tell me the procedure on how to get the transmission mount off.

Thanks

First try swapping both front tires to the back. If this eliminates or alters the vibration, you have a wheel or tire issue. Only takes a few minutes to try. You mentioned rebalancing but didn't make mention of rotating them...

Next, get it up on a hoist and perform a very thorough inspection of all front end and steering parts. If you're unsure as to how to do this, have a trusted shop do it. These vibes can be coming from SO many different things. Troubleshooting them online is very difficult. Inspection is critical.

I had a vibe between 55-60 on my 99; on and off. Ended up being a bad ball joint and I replaced the steering stabilizer while I was under there. The stabilizer generally is not a "root cause" of vibrations but let's face it; most of our Jeeps have parts that have a bit of play in them and the stabilizer can help dampen some of the resulting light vibrations from those parts.

Good luck and post back what you find....