Can I get an alignment before rear control arm replacement?

[GitEmSteveDave]

Short story long, recently I've been traveling 50+ miles each way daily to visit someone and in the rain at highway speeds(above 60 mph), through the seat, my Libby feels loose. I didn't feel it in the wheel, but in my butt. Then later that night while getting on the Parkway, the rear slid out from underneath me, and I fishtailed a second or two, but recovered. I kept it under 60 the rest of the way home, and luckily I haven't had to take her out on wet roads, at speed, since. I bought the tires in 2020, have 55,000+ miles on, and they're all a thumbnail away from the wear bar

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so I decided to replace them all, because one was plugged in 2023 and another has a intermittent slow leak I can never seem to source. I'm getting the tires tomorrow.

But I also wonder if maybe my rear control arm(s) have finally given out. I know when I bought it, my mechanic said the boomerang was fine, but the lower control arms were a little rusty. I also ran over a piece of rebar a landscaping truck dropped with my front passenger tire and heard it bounce it's way down my undercarriage a week back. I pulled over and made a visual inspection, but didn't notice anything and there have been no major difference in drips and drops in my parking space(Bless those skid plates) I made an appointment with a new mechanic on Wednesday(my old mechanic is no longer close to my job, so it's not easy to drop it off and pick it up after work) for an oil change, so I'm gonna ask him to check the arms and if he sees any damage from the rebar.

My question is, I've never had her aligned in the 6+ years I owned her, so I was gonna do it at the tire place. If I get it aligned, and then need new control arms, will that screw up the alignment?

 

[u2slow]

The alignment is done on the front.

There is nothing to adjust on the rear.

 

[KJowner]

Old tyres can be nasty, however on a KJ a worn ball joint on the front can make the handling awful, jack it up corner at a time and have a good wriggle on the wheels, any movement or knocking needs looking at, be really thorough, most issues are front end related. Check for steering gear wear as well.
Worn rear lower arm bushes let the rear axle steer. Especially noticeable with a heavy trailer on the back... makes you grip the seat with your rear end when you hit a bump going round a corner and the Jeeps rear suddenly steers itself! (Been there!)
If the rear bushes are shot to bits then the axle may be wondering about, the only thing that aligns it is the lower arms, the lower arm body side bushes aren't solid, they have voids ls to allow movement, unfortunately the rubber splits into the voids letting them flop around.
The top arm just stops the axle moving back and forward as you drive, this usually gives you heavy thump from the rear as you speed up or slow down.
The other thing to look at is the springs and shocks, if they are original they are probably very worn, what's the measurement from the centre of the wheel to the underside of the wheel arch?
An alignment certainly won't hurt but loose handling suggests something is worn out, I'd get that sorted first and then align it so you don't wreck your new tyres or have to pay twice.