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I am replacing the front control arms on my vehicle (ball joints and the bushings are more than well-worn after 20+ years of service). But I am finding myself in somewhat of a predicament: all of the hardware currently on the vehicle will be reusable when I go to install the new arms, except for the slotted nuts securing the ball joint, due to excessive rust and corrosion. And the replacement arms did not come with new hardware.

I have tried to no end to find replacement nuts with the correct thread size and thread pitch - through my own dealer, 2 Nissan dealers, 5 auto parts stores, and 7 hardware and hardware supply stores. Nothing. It's as if it doesn't exist.

Thus, my question: it has become known to me that many replacement aftermarket parts, and even OEM manufacturers, are now using nylon lock nuts on ball joint studs; but in this scenario, would it be acceptable to use a nylon lock nut instead of the traditional slotted nut & cotter pin when the latter is technically called for? The studs on the replacement arms do have holes drilled in them to accept a cotter pin.

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  • Try ebay, it's amazing what you'll find on there. Also, no reason you can't use pins with lock nuts as extra protection.
    – GdD
    Feb 21, 2022 at 17:56
  • I'm assuming these fasteners have a Nissan PN. Do you know it?
    – jwh20
    Feb 21, 2022 at 22:36
  • Whenever looking for hard to get parts I try some British car-part shops. There are many (with online presence and that will ship abroad) that are well stocked and there is also a surprisingly huge after-market replacement part supply chain in the UK.
    – Tonny
    Feb 22, 2022 at 9:18

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You really need to find slotted (castle) nuts for the application. The specific reason for this is, castle nuts have a positive stop (the cotter pin). It is nearly impossible for these to spin off when put together correctly. Conversely, a nylock nut can fail. If one fails on your steering/suspension components, the failure will be catastrophic. It is not a given it will fail, but even if it's 1 in a million chance, do you want to take that chance with you, your family, or those around you? You're far better getting replacement castle nuts.

To find them, the easiest places to find them would be places like McMaster Carr or Fastenal. Both have a large diversity of fasteners where I'm sure you can find what you need. (NOTE: I have no affiliation with either company.)

As far as your assertion companies are going to Nylock type fasteners for these, I've never seen them. Plus, I'd never use them in this situation. IOW: Use at your own risk.

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  • Going through some old posts... I ended up using Nylock nuts for this repair - couldn't find a castle nut anywhere. It's been close to 2 years with the new control arms installed on the vehicle and they've not budged a millimeter. I did install cotter pins on both arms for "added protection." Curiously, after a few years of working as a repair technician, I have found that the use of Nylock nuts in place of a traditional castle nut, is actually fairly common; Chrysler/Stellantis in particular seem to use them quite frequently, even on some of their trucks. Mostly on late(er)-model vehicles. Sep 27, 2023 at 3:11

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