When you say the upper mounting nut, do you mean the big one in the center of the strut or the smaller ones that hold the strut mount in place?

 

The big one. Unless you have a crows foot or an open end torque wrench, it is practically impossible to accurately torque that thing, as you have to hold the strut stud to keep it from spinning with the nut (very common with stupid McPherson struts).

I cranked that nut down with a ratchet and actually put the correct torque on it (believe it or not!), but apparently the stud was spinning enough to deceive my torque wrench .

Once I got that dogbone on it that allowed me to crank the nut down some more while holding the stud still with an allen wrench, I got another 3 threads showing and the clunk went away altogether.

It's just a stupid aggravating design that I wish they'd do away with on all vehicles. It is so nice changing normal struts with normal side-mounted lobes where you don't risk trashing your brand new strut trying to torque it.

 

I replaced the struts awhile ago. Since they were drop in units it never occurred to me that I should torque the large nut on top. I'll check it out.

Curiously the issue I'm dealing with only occurs with weight on the wheels (eg putting the car up on jack stands and putting it in gear shows no odd noises or clunks). Your comment in an earlier post here about only occurring with weight on the wheels may be the tipoff I've been looking for.

What is the torque spec for that big nut on top?

 

76 lbf, per Chiltons

and 46 lbf per AllDataDIY, so ymmv. I smoked mine down to about 80lbf.

This is the tool I used. It's a metric nut, if I recall correctly, but the equivalent SAE socket will *just* hold it enough to torque, as the metric version of this does not get big enough (I might have that backwards though). You'll want to check the nut size with a socket before buying it to make sure I didn't get that backwards (I can't remember if I bought the metric or SAE version).

Again, you can torque it without holding that ball stud with an allen wrench, but the torque is deceiving and leaves enough slop to make a noticeable clunking noise going over bumps. If you hold that ball stud, you'll be amazed how much more torque you can actually put on it before hitting 70-80 lbf.

**EDIT**

These are the FRONT struts I am referring to, of course. You mentioned "dropping in" your struts, which you don't really do with McPherson, but is the case with the rears, so I want to clarify that it is just the front struts I am talking about.

 

Roger the drop-in comment... I use that since it comes as an assembled unit. I suppose the more accurate words would have been "lift in!"

Appreciate the torque value. Enabled me to find it in my shop manual. See pg 204-01-10, Front Suspension. Strut & Spring Assembly Step 3 reflects 76 lb-ft.

Since it came assembled I never thought to check the as assembled torque value of the rod-to-bushing nut.

One thing that has baffled me with this clunking is with the car up on jack stands the weight remains on the suspension struts (& therefore the sway bar links). If you have an idea why being on wheels makes a difference in the weight the strut & sway bar links feel I'd appreciate your thoughts.

That said, I roger up for the fact that the noise goes away when on jack stands versus on wheels... just figures!

I've seen my share of oddities like that across my time working on things mechanical over the years.

 

So you bought the pre-assembled unit-- got it. I forgot they sold that, as I had just bought the individual strut.

As for your question, I would look at anything that lifts up while the vehicle is on the ground. In the case of that strut-to-bushing bolt, it appeared tight (especially with the vehicle jacked as the springs extend that strut as far as it will allow, thus pulling it tight against the bushing), but when placed on the wheels, the spring contracted. Thus, going over a bump allowed for the strut to travel upwards just a fraction of an amount, but enough to make a very noticeable clunk when the springs extended again coming off of the bump.

So whether yours is that particular nut or not, I would look at anything else on your vehicle that could also move under compression (ie weight-on-wheels, traversing bumps or lateral shifts), rather than just looking at pure tension (ie jacked up in the air with gravity extending everything).

A few things that come to mind apart from suspension are:

- engine mounts
- exhaust mounts
- steering column
- steering knuckle
- half shaft components
- tie-rods

 

nicknc: when I place the car up on jackstands I put them under the wheel knuckle arm such that the weight of the car is on the suspension. The only things not feeling the weight are the wheel bearings and calipers.

Thus this one has baffled me. Will checkout the sway bar links. Any other ideas?

 

I'd still look at the items I mentioned and just rule them out one by one. There is a lot that can clunk when not properly torqued-- I'd start with the most common culprits, especially those easily checked.

Suspension and wheel/axle components are designed to move a lot during the course of driving making them more susceptible to premature failure.

I troubleshot the hell out of a steering wheel vibration recently that wound up being a warped wheel, of all things-- something I did not consider, but given the symptoms, should have been a logical cause.

 

Roger that... I'm working down the list. Just hoping to avoid "throwing parts" at it.

My Sway bar links are due for replacement so that's next on the list.

 

Well... It's in the strut (drvrs side).

I split for a Steelman remote sound sensor system. Got it from Tooltopia.

Put sensors on the brake caliper, transaxle, lower arm, and at the strut midpoint where the sway bar link attaches. No noise from the caliper, a nice rotational hum-m-m from the transaxle.

The lower arm showed some of the cyclic knocking. The strut midpoint sensor very clearly had the knocking.

Will put the sensors more specifically on the strut to see if I can pin in on where the noise is coming from.

Anybody out there got any experience here? The knocking I have is same as the wheel rotation, disappears on coast & hard acceleration and with steering input in either direction.

What I don't get is the synchronism with wheel rotation. I see no indication of the wheel contacting anything and I've swapped wheels side to side with no change.