Do it this way to save some labor for future maintenance. Installing a cotter pin.

Lower Ball Joint Cotter Pin
Ball joint cotter pin. Need some advice on tightening down ball joints and tie rod ends. The constant cycling at that point would fatigue the bolt in no time and it would fail anyway. Insert the cotter pin into the hole of the bolt until the head of the pin rests against the bolt. Secure the cotter pin by spreading the prongs in opposite directions using pliers if desired. Yeah they have nylock nuts but their kind of small where the stock bolt is more of a washer castle nut combo. The new ball joint had its own cotter pin which also of course keeps it from backing out anyway.
A cotter pin will not prevent the bolt from failing if it does back out to the point that the cotter pin is actually doing something. Most of the time. Other designs have a self locking nut that doesnt require a cotter pin. Get free shipping on qualified cotter pin pins rings clips or buy online pick up in store today in the hardware department. The most difficult part of removing any ball joint is disconnecting the taper fit stud at the end of the joint. Replacing an f 150 blend door actuator for hvac 2009 2014 removing a miata engine.
The ball joints without cotter pin holes that ive used always had nylock nuts with the ball joints. There will be no grease zerk to install if you got a lifetime joint. Use diagonal cutters to cut excess length from either prong according to your application standards. Most of the time you torque the nut down insert the cotter pin and then bend the pin around the castle nut so it wont work loose. Some ball joints have a cotter pin which is used as a safety device to keep the nut from coming off and the joint coming undone. Im working on a car where my replacement ball joint nut tightens down below the cotter pin hole.
The upper ball joint castle nut is tqd 50 90 lbs per manual specs and the cotter pin goes through where it is supposed to go as in hole and slot. Crown vintage ball joint cotter pin item weight 16 ounces product dimensions 275 x 275 x 075 inches item model number j8121392 exterior machined manufacturer part number j8121392. Not vital but the way cotter pins were intended to be installed. The lower ball joint castle nut is tqd the same but the cotter pin is way high and does not go through the castle nut and hole together.