Shaking

I have an 04' KJ Columbia with a 3" lift, and when driving at around 60-70 mph, the car shakes pretty bad, but after 70, it drives okay. Is this a drive shaft or U-joint issue, or wheel related?

Could be any of them. Easy stuff first. How are your tires? Wearing okay? Balanced? Aligned?

Start with the tires being balanced. Sounds like a balancing issue to me if it eventually goes away at speed and doesn't get worse the faster you go.

The tires are basically brand new, Goodyear Wrangler A/T's 245/75/r16s, tires were balanced when they were changed and are wearing well. As far as alignment, I've had it off-road a bit so it could be a tad off, but it doesn't seem to pull any particular direction.

Jack up the front end and check for play in the ball joints, wheel bearings and tie rods maybe.

Yeah I'll look into that, it most likely needs some tlc in that area as I don't know its history other than for the time I've had it. I bought it about 3 years ago with some mods already on it, so I'm still learning things about it that have been done.

I had a similar issue once, along with eratic steering on some uneven bits of road, was steering alignment. I'd start by checking steering components the hen alignment and balancing, as mentioned above.

Might want to double check those new tires balancing, were they done on a modern digital balance machine?
Also a good idea to check steering rack bushings too. Get someone to turn the wheel a quarter turn back & forth while observing the rack bushings...
Mine had upward & side movement bad, rubber was split from wear.
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That’s was the beginning of the end for my driveshaft
It would have vibes from about 20-40 nothing from 45-50 then 55-65 vibes like crazy until over 70 then it’d be gone
Believe me, you don’t want it to give out on you while driving down the freeway.. not a pleasant sound or experience!
Seems that 3”+ lift kills it fast if you don’t have aftermarket parts to correct the sharp angle