my dad noticed that my jeeps rear drivers side wheel was wobbling while I was driving.
I tightened the lug nuts and installed the spare and it is still wobbly.
anyone have any idea on what it might be?
Probably the hub assembly or ball joints, possibly both.
Hub is easy enough to check, just pull off your wheel and rotor, and see if there is any play in the hub. It should rotate, and do nothing else. If it wiggles even a tiny bit, replace it.
And here's about ball joints- http://m.wikihow.com/Check-Ball-Joints
There are no bolts holding the rear axle in place, the axle shaft is held in with a c-clip, you need to lift the rear of the jeep, put it on a jack stand or use a floor jack (for safety) and spin the tire in question, if you see it move side to side as it turns it's most likely a bent axle shaft. This is easy to fix, a new shaft is not expensive, a new axle bearing, seal and you get to change the oil in the diff, take advantage of the opportunity and upgrade to alloy shafts, a nice upgrade.
There are a million ways to build a Jeep, pick one and do it - you bought a canvas, not a painting!
This is a long shot...
Do you have aftermarket rims on your Jeep?
Jeep put clips on the wheel studs to stop the brake drums falling off in the factory.
The clips remain on the wheel studs because OEM Jeep rims have a cut-out to allow for them.
Aftermarket rims may not have the cut-out and the if the clips are still on the rear wheel studs, the rim won't sit properly.
The clips caused my rear lug nuts to come loose when I switched to aftermarket rims.
A new axle shaft will require a new bearing pressed on, and a new seal.
You mentioned it was only noticeable when your Dad was following you. As long as you can't feel it inside the Jeep, you don't hear anything back there (bearings), or you are not leaking fluid past the seal, I would keep driving it.
But mines not a DD either.
The only vibration I feel is on the highway when I reach 70+. It's a small vibration coming out of the rear..... I think it is that. I am going to pull the tire, caliper, and roter off to see if it is the axle shaft before I tear it all apart.