I have installed new upper ball joints on my 2000 four wheel drive Olds Bravada. On the drivers side the castle nut is not tall enough to engage the cotter pin in the slots. Can I put a flat washer under the castle nut? Or do they make a taller castle nut? What is the thread size for the ball joint stud? Both the left and right castle nuts are the same height. Any help appreciated.
RTJ49

 

Welcome to parts made in China . I had the same issue when I replaced the ball joints in my profile pic. my 4x4 rx7.

The replacement ball joints were Moog so even the better brands can have problems.

While you could use a washer too bring the nut up I did it the harder way, I torqued the castle nut to proper torque then redrilled the shaft to insert the cotter key

 

I'd go with drilling a new hole. If you use a washer below the nut it would need to be a hardened one like grade 8.

 

Can you reuse the old castle nut?

 

With mine the nut was the same the stud was drilled to high