C3 Lock Nut Questions

[Michael C.]

I'm about ready to reinstall my refurbished front suspension and steering, but have a couple questions about lock nuts, prevailing torque nuts and/or crimp nuts. I've seen these assorted names to applied fastening devices in various places.

The nut and bolt on the left side in the photo below are new and are for the rear end of the lower control arm shaft. I purchased a pair of these from one of my favorite vendors. Although new, I was unable to get the nut beyond the position you see when I tried to attach the shaft to the frame. Same story with both nuts and bolts. I think I understand the intended function of this type of nut (and don't expect to finger tighten them), but I don't understand why I can't get the nut properly tightened. After running into this issue while attempting to install the shaft, I decided to see what would happen with the unused bolt and nut off the car. Same problem. In fact, the nut in the photo is so tight I can't get it off the bolt. I was finally able to get the first bolt and nut off the car. Someone suggested I use some anti-seize and this did allow me to get the nut further onto the bolt (while off the car). I didn't go more than a couple of threads beyond the nut because I didn't want to end up with another useless bolt and nut. Before and after my attempts the threads on all pieces looked fine. And I'm sure I didn't cross-thread the nuts. I'll order another set of bolts and nuts from a different vendor. Any suggestions of how to avoid the same problem?

The lone nut in the photo is for attaching the steering arm on the spindle. This appears to be another form of locking nut and looks like one shown in a NCRS judging manual. Several vendor offerings look like the one on the bolt in the photo, only smaller. All of the nuts that came off the car appear to be in good shape, so I might just reuse them with new bolts. What is the correct design? Thoughts?

Thanks all,
Mike
LockNuts.jpg

[Joe L.]

Re: C3 Lock Nut Questions

I'm about ready to reinstall my refurbished front suspension and steering, but have a couple questions about lock nuts, prevailing torque nuts and/or crimp nuts. I've seen these assorted names to applied fastening devices in various places.

The nut and bolt on the left side in the photo below are new and are for the rear end of the lower control arm shaft. I purchased a pair of these from one of my favorite vendors. Although new, I was unable to get the nut beyond the position you see when I tried to attach the shaft to the frame. Same story with both nuts and bolts. I think I understand the intended function of this type of nut (and don't expect to finger tighten them), but I don't understand why I can't get the nut properly tightened. After running into this issue while attempting to install the shaft, I decided to see what would happen with the unused bolt and nut off the car. Same problem. In fact, the nut in the photo is so tight I can't get it off the bolt. I was finally able to get the first bolt and nut off the car. Someone suggested I use some anti-seize and this did allow me to get the nut further onto the bolt (while off the car). I didn't go more than a couple of threads beyond the nut because I didn't want to end up with another useless bolt and nut. Before and after my attempts the threads on all pieces looked fine. And I'm sure I didn't cross-thread the nuts. I'll order another set of bolts and nuts from a different vendor. Any suggestions of how to avoid the same problem?

The lone nut in the photo is for attaching the steering arm on the spindle. This appears to be another form of locking nut and looks like one shown in a NCRS judging manual. Several vendor offerings look like the one on the bolt in the photo, only smaller. All of the nuts that came off the car appear to be in good shape, so I might just reuse them with new bolts. What is the correct design? Thoughts?

Thanks all,
Mike
[ATTACH=CONFIG]111087[/ATTACH]

Mike-------

Both of the nuts you picture are distorted thread lock nuts. a type of prevailing torque lock nut. The style shown on the bolt is sometimes referred to as a "stover nut". This is the type that was originally installed on my original owner 1969 for the application you describe and is the type that GM used for most lock nut applications during the period. The GM part number for this nut was GM #9422302 but it's discontinued from GM.

Either type of nut will thread easily onto the bolt for a few threads----right up until the distorted thread portion of the nut is reached. Thereafter, considerable torque is required to further turn the nut onto the bolt. From just your description, I cannot assess whether there is some sort of quality problem with the bolts and nuts you have. Just understand that considerable torque is required to turn these nuts down on the bolts.

[Michael C.]

Re: C3 Lock Nut Questions

Thanks Joe. At 75 years old I hope that I will be able to apply the considerable torque

[Mark F.]

Re: C3 Lock Nut Questions

Thanks Joe. At 75 years old I hope that I will be able to apply the considerable torque

Some estimate that adding a lubricant could reduce the required torque reading by up to 40 percent!

http://www.smartbolts.com/insights/i...%20efficiently.

[Michael C.]

[Joe L.]

Re: C3 Lock Nut Questions

Attached are photos of an NOS GM #9422302 lock nut. As I previously mentioned, this is the nut used for the 1968-82 steering arm attachment.

DSCN3992.jpgDSCN3994.jpg

[Mark F.]

Re: C3 Lock Nut Questions

Attached are photos of an NOS GM #9422302 lock nut. As I previously mentioned, this is the nut used for the 1968-82 steering arm attachment.
[ATTACH=CONFIG]111140[/ATTACH]

Hi Joe,

Excellent photo...you can see the result of sequencing the machining process whereby the nut was clamped (resulting in the dimple marks); and then clamped again distressing the "V-shaped" areas which are crimped (pushed into?) the bolt path distorting the last threads to create the resulting locking force (probably all done in a screw machine that made the nut).

I noticed (I think) the date on your label is "rev 10/81".

It would be fascinating to see a photo of where you keep all of your NOS GM stuff you have purchased over the years!
I read an archived string where you said you set out to buy GM parts before they became "unobtainium" (my words) - and it sure looks like your collection is deep and broad!

[Michael C.]

[Gary B.]

Re: C3 Lock Nut Questions

AMK Products sells a repro of GM 9422302, cad plated, which is nice.

1ED8FD17-9BA6-4B39-9E8F-E46B9E97E61B.jpg

You can also find NOS examples of 9422302 on eBay right now. Not cheap.

Gary

[Michael G.]

Re: C3 Lock Nut Questions

GM lock nuts were “tuned” by the manufacture to have a certain maximum “prevailing torque”. This torque is significant, but it is nowhere near the load you will apply in torquing the joint, so you should be able to easily overcome it by hand.

In the sixties, the manufacturer of these nuts would would have a standard “crimp” that deformed the first few threads, thus creating the prevailing load. They altered this crimp as necessary to adjust that prevailing load. The nuts were cadmium plated, which is a very slippery finish, and they also applied WAX to the threads to prevent galling and adjust the load more accurately.

In your case, given that these have no requirements to meet GM’s Specs, the likely Chinese manufacturer may have over-crimped them or plated them with with zinc (a very high friction finish) or applied no wax or other lubricant (or all of those things). You could try lubricating them, (it won’t hurt anything, as you obviously now have way to much friction to create too much load and fracture them) but if the prevailing torque can’t be overcome with 10 FT-lbs, by hand, it will affect your clamp load too much and I would not use them.