Does your TJ hum on the highway?

[Hopper]

Just bought this 99 TJ 101,000 miles on it. Needed a 2nd runabout since my F250 is staying on more jobs these days.
Me and my daughter love driving it around town although my wife says it's to "jerky" .
Haven't driven it alot but noticed a few things.
1. It cranks up hard not violent just a quick low shake and hums and cuts off with the same shake hum when I shut her down.
2. At about 60 mph we get a good vibration happening. I dont feel it in the steering wheel, but the seats feel kinda like one of those vibrating chairs at the mall.
3. When I back out of the drive and get on the main street facing a decent hill I put it in drive hit the gas and it almost dies, after driving this does not happen again.
All in all it's not horrible and I love owning this Jeep just not sure what's a Jeep Thing and what's not.

 

[-T.]

Do you have any maintenance history?
I'm not sure about the hum at startup and shut down, but the almost dying issue and maybe to some degree the shake at startup and shut down, as well as general driveability could be improved by cleaning or replacing the Idle Air Controller. And maybe the throttle position sensor, although I kind of think it would be throwing a check engine light if this was having problems.
https://wranglertjforum.com/threads/how-to-clean-your-iac-idle-air-controller-valve.662/
I've been surprised by the improvement I've seen by doing this.
The vibration at 60 mph? Maybe a worn U-joint? You didn't mention if the Jeep was lifted. If so, it could be a driveshaft angle issue.
Also, the engine shaking on startup and shut down? Maybe engine mounts?

I'm just spitballing here. Good luck!

 

[bromel]

Vibration at 60 is most likely unbalanced tires. You mention in your profile a mild lift... was the transfer case lowered? If not, that might account for vibrations, but the classic unbalanced-wheels wobble happens around 60, so I'm guessing that is the culprit.

 

[Hopper]

Thanks. Was just watching a video on pinion angles. Going to inspect the motor mounts in a bit. Wish I new more about mechanics. Think I found a good Jeep mechanic that can do a walkthrough and let me know more about what I got.
Think you may be right about the angle.
Definitely new tires this week.

 

[Chris]

Humming is usually loud tires, which is an inherent trait of the type of tires we typically run.

A cyclical vibration (with an up and down to it) is something entirely different, though it does sound like a "hum" on the up portion of the wave.

A vibration in your seat that is constant is almost always caused by improperly balanced tires, and then driveshaft / pinion angle.