Do I need to remove the axl in order to remove the castle nut from the top of the ball joint? Or could I tap the cotter pin out and try to use an open wrench on the castle nut?

 

You can do what you stated, just use an open wrench on it. There's a Youtube tutorial where one individual ended up grinding down his wrench so the box end fits.

 

I am confused about your post.

Low ball joint:
Straighten pin.
Loosen castle nut.
Remove the other two fasteners [1 nut and 1 bolt if I remember it right, or 2 bolts, or 2 nuts].
Loosen the castle nut till it is in level with the bolt.
Loan or purchase the tool to separate ball joint [do not use a pickle fork]. Some mechanics have a knack to hit the side to free the center bolt, I rely the separator tool. break the bind and then remove the castle nut. [if you you are going to use a new boot, then you can use the pickle as it will rip the old boot].
I always use a fresh pin, and many reuse the old one.

[Note for suspension related stuff, I always use two jack. The second jack helps apply/take tension of the spring. Just remember not to put lift force through the spring. It is ok to compress the spring 1/2"].

Salim
PS: If you remove the rotor, mark its position on the stud. You should reassemble based on the mark.
I dont remember having access issue. You can change the angle of the hat shaft by lifting the vehicle.

 

They're asking if they need to remove the CV axle in order to get clearance to the ball joint castle nut, or just use an open ended wrench, instead of having to remove it; there isn't much space there.

 

There is enough space to access the castle nut. Socket can't be used but no issues with a wrench. You would need a crows foot for proper torquing [Math my be needed if the 90degree position can not be set]
The other end has 3 fasteners. [1 bolt 2 nuts?]

Salim

 

https://youtu.be/3EurTqgXpn0

This is a different model of lexus but almost exactly the same situation. The 3 minute mark shows it well.

My box wrench is too thick to fit and I'm afraid of rounding the castle nut if I use an open ended wrench but I'm thinking an open ended wrench might still work.

 

No matter what you do, never use open end wrench on any nuts, unless it is already very loose. You WILL round the nut and then what?
Grind down box wrench, like in vid link. Heck, lock good vise grip jaws on it. New ball joint comes with new nut anyway.
Loosen the nut with box wrench. Now, here's the tricky part. Weight of the vehicle is on that ball joint stud and control arm. Weight is directed down, locking stud in the knuckle. So CA needs to go down or hub needs to go up to clear stud.
This is what I did before several times. I used scissor jack that comes with the car, to place it directly under the rotor center. Wheel removed, 3 through hole lug nuts to secure rotor to the hub. Lift entire vehicle front at the front jack attachment point, there is one. Also, secures vehicle in place in case something goes sour. That's for hydraulic jack.
I will remove cotter pin, loosen the castle nut as far as it goes, take heavy hammer and hit few times very hard on the knuckle. That pops stud loose.
Now, you need to move the hub up somehow, so that stud comes out of the knuckle.
Then, I placed scissor jack platform directly under the rotor center. Slowly start jacking rotor+hub up. As I do so, stud starts coming out of the knuckle DOWN, so I keep undoing the castle nut. Until it's completely out. Then it's pry bar or foot to separate the two.
Had it done - trying to think - 3 or 5 times. On various cars. But it's a two jack job. One supports entire front weight, one lifts hub up.

 

I have a tool which looks like this.
https://www.ebay.com/p/NEBO-5558-Gri...hm=1000&chn=ps

Never had problems with rounded nuts.

1. Take box wrench from harbor freight and grind it down,
2. Use the open end wrench. I have never had problem with ball joint nuts as they are never torqued high and the binding is with the cone of the bolt [Remember the ball joint spins/rotates, that is why they are pinned]. I have had proles with the ball joint shaft spinning [not binding].
3. Never hit the ball joint without having the nut on to protect the threads. Undo the nuts and protect the tip threads.

Salim