My front struts are loose and I can't tighten or even remove the center nut no matter what I do; even holding the strut piston shaft. The center nut is mangled from the threads, i guess the plastic inside. It just spins by hand. I'm going to try drilling it with a hole saw. What's the thread size to replace them? Thanks.

Is this strut assembly still in the car or out?

Unless you have it firmly in a spring compressor with some compression (out of the car), NEVER do anything with that center nut. This can get very messy and you can get very hurt.

How old are the struts that they are presenting problems? Original or aftermarket?

Thanks for your concern but the struts are still installed. They still work. I just cross threaded the nylon nuts with the impact wrench I'm guessing, and they just spin freely without backing off or tightening.

I really need an alignment right now. Its important I can replace these nuts.

I would use a cut off wheel to extract the nut off.

The nuts should be made out of metal, not plastic. Probably what you are looking at is the thin plastic locking band.

Like lux97Max said, cut the nut off or use a nut buster. However, I think you have a good chance of discovering that the threads on the strut rod are fubar.

Darn. Oh well, they're just ebay yellow struts. I'm still going to try replacing the nuts. I hope I can find the right thread size.

Yup I managed to back off one nut. Strut threads mangled.

Edit: I guess my next question is: can I fix the threads or stack a bunch of washers? Doesn't sound safe.

You might get lucky and be able to fix the bad threads with a tap and die set. But first you'll have to determine the actual thread size and pitch.

Problem solved. I went to the junkyard and got oem nuts. They went on pretty forced but they're on tight. Those nuts that came with the struts originally looked way too cheap to be automotive grade. Lucky me.

Congratulations! You are LUCKY.