Intermittent (suspension?) rattle from left front on '01

TL;DR: I'm getting a rattling noise, intermittently, from somewhere in the left front of my '01. I replaced the left CV axle and that's not it. I did some inspection and prying around and I can't convince myself that it's the ball joint, sway bar, or sway bar links.

What could it be?

Caution: Long post ahead.

Long version:

History:

2001 with a bit over 250,000 miles on it. USA model, left-hand drive.

Both factory front struts were replaced (by a mechanic) with new KYB front struts at roughly 180,000 miles, but I don't know if he replaced the strut top mounts (triangular-ish plate with bearing) at that time.

New front tires (Generals, by a tire shop) at about 228,000 miles.

Both factory front sway bar links were replaced (by me) with Toyota parts at about 230,000 miles.

Characteristics:

A few hundred miles ago, I started to get a rattling noise that sounds like it's coming from the left front somewhere.

It doesn't always start as soon as I start driving. It can start "on its own", or after I go over a small or large bump in the road.

It can happen at anywhere from a few miles per hour on up.

Once the rattle starts, I can keep it going or even make it a bit louder by steering to the left. Steering straight keeps it going. Steering to the right quiets it down. These are all "normal lane change" amounts of steering, not "trying to keep in one lane" amounts of steering.

Once the rattle starts, it keeps happening if I'm driving uphill, on the level, or downhill.

Once the rattle starts, it keeps happening if I accelerate, coast, or slow down with the brakes. If I brake the car to a stop, the rattle stops around maybe 2 mph.

It's a fairly fast noise, maybe 2 or 3 Hz. It is a little bit correlated with road speed (rattles slightly faster if I drive faster); it's not correlated with engine speed.

I don't feel it in the steering wheel if it's not very loud. If it gets real loud, I feel it a little bit in the wheel.

It doesn't try to jerk the wheel out of my hands. It might cause a slight "shimmy" feel - as if the front end of the car is "wiggling" side to side - but I'm not 100% sure of this. I always feel like I still have control of the car.

The rattle is a little bit correlated with temperature. If the car has been sitting outside and it's been below 60 F (15.5 C) for a while, it's quiet as I first start driving it, but the rattle may start after I've driven it for a few miles. If it's over that temperature, the rattle seems to start sooner.

Sometimes the rattle doesn't happen at all. I drove it 8 miles this afternoon in 70 F (21 C) weather, and it was absolutely quiet the whole time.

What I've tried:

When the noise started, I jacked up the left front, took off the wheel, and inspected.

I noticed that the outboard CV joint boot was torn at the small diameter - right next to the clamp. It had been slinging grease on the top of the control arm, back of the wheel hub, etc. The inboard boot wasn't obviously torn.

I could move both sway bar link ends by grabbing them with two fingers and turning them. (The old ones that I replaced a few years ago were too stiff for that).

The outboard end of the sway bar itself is kind of rusty - from a few inches outboard of its rubber mounting bushing, to an inch or two before the end where the link bolts on. I looked it over and it's not rusted through, and I didn't see any major cracks, but I might have missed one.

I couldn't make any noises or play happen by grabbing the spring with both hands and trying to turn it (like steering the car), or by pushing inboard or pulling outboard on the spring. This was with the suspension at full droop.

The brake-caliper-to-bracket and bracket-to-hub bolts were torqued correctly.

The strut-to-hub bolts were torqued correctly.

The ball joint nuts and bolt (bottom side) were torqued correctly. The cotter pin was present in the tie rod end nut.

I tried prying between the lower control arm and the hub with a pry bar, and I didn't notice any movement in the ball joint.

The bolts that hold the sway bar bushings down to the subframe are at least present and not totally loose - I couldn't get the torque wrench on them, but I got a regular ratchet and socket on them, gave a good twist, and they didn't move.

I also put the left front wheel+tire back on, put one end of a five-foot (1.5 meter) 2x4 on the ground a few inches inboard of the tire, pulled up on the outboard end of the 2x4, and I didn't notice any movement in the ball joint.

Finally, I jacked up the right front, took that wheel off, and took a look around. It passed all of the same tests.

The right side also had a torn outboard CV joint boot, at the small diameter. It had also been slinging grease, but maybe not as much as the left side. The inboard boot did not appear to be torn.

I also noticed some heavier tread wear on the outboard edge of the right front tire - about 22,000 miles on it.

Changes that didn't fix it:

Because of the torn CV joint boot, the grease, and the dependency on which way I was steering, I decided to try replacing the (factory) left CV axle complete. I got a new complete axle from NAPA, and after some travail getting the big nut on the end of the axle loose, I got the old one out and the new one in. In doing that, one of the two ball joint nuts stripped out, so I replaced both nuts with "generic" metric nuts from the car parts store.

Unfortunately, the new axle didn't seem to change the rattle much.

Possible actions:

The place on the transmission where the axles connect is closer to the driver's side of the car, so I'm trying to convince myself that it could be a problem with the inboard CV joint on the right axle. I have a new replacement axle for that side, but I haven't installed it yet. I feel like the noise might be coming from further outboard than that, though.

I am also suspicious of the strut top mount on the driver's side. It appears to have a ball bearing in it, and it has occasionally made noise when turning at low speeds (like in a parking lot) before. Maybe it has worn enough to let the strut assembly move either up-down or inboard-outboard when driving, and that's the noise I hear. I will probably at least take the wipers off so I can check the three little mounting nuts, and the big nut that holds it
to the strut.

Go nuts and replace the lower control arm, ball joint, sway bar link, strut top bushing, and maybe the whole strut and the wheel bearing.

I'm willing to listen to any other ideas.

Thanks!

 

tl;dr: It turned out to be the right side CV axle, with a sprinkling of a crappy General RT43 tire.

Long version:

When I set out to fix this, I bought both CV axles from NAPA. In the post above, I had only changed the driver's side one. That changed the noise, but didn't eliminate it.

A couple of weeks ago, I replaced the passenger side axle... and also bought two new tires. That totally eliminated the noise.

After I replaced the driver's side axle, I still got the noise whenever the front wheels were turning. It kind of sounded like it was coming from the middle of the front of the car - like, where the axles go into the transmission - instead of near the wheels.

I had also noticed that at very low speeds - like backing out of the driveway, or pulling into a parking lot - the steering wheel would deflect a few degrees on its own, in one part of the tire rotation. I chalked this up to a worn ball or race inside the CV joint that was sticking and then coming free, although in hindsight, I think it was the tire.

What finally pushed me to replace the other axle is that I got on the Interstate, and the noise and vibration had become much more intense when I got up to 65 mph (105 km/h). It was bad enough that I cut it to 60 mph (95 km/h), took the very next exit, and completed my trip at 35 mph (55 km/h) on the city streets.

When I set out to fix it, I took the passenger front tire off... and discovered that in one spot, the steel belts had worn through the tread, and were also poking through the sidewall at that point. It was a General RT43 tire that I had bought new in late 2019; it had about 4.5 years and 25,000 miles on it, but was completely junk. On either side of the belts, there was a "bubble" (delamination?) in the tread. As soon as I saw the damage, I found a stick and jammed it in the valve core to let almost all of the air out.

I proceeded to replace the passenger-side (longer) CV axle. Along the way, when trying to loosen the nut on one of the (factory original) ball joint studs, the stud just snapped off, so I also bought a new ball joint. See below for comments on the fasteners on the ball joint.

When I got it back together, I put the donut spare on the right front, because I didn't trust the General to make it to the end of the driveway. I took a short test drive and the noise seemed to be gone, but I didn't want to trust it until I had a full-size tire on the front.

When the tire store opened, I took it there, and then found that General's mileage warranty is also worthless; the kid claimed that my tires were worn too far for it. Also, General RT43s are such junk that General retired that model and replaced it with the RT45. I wanted not-a-General, so the kid steered me to some Falken Sincera tires, which I bought two of.

(What I really want is the Michelin Harmony tires that I ran in most of the 2010s - the best tire I've ever had on this car - but Michelin stopped making them in Gen1 sizes.)

Once the new tires came in and were installed, I did some real test drives... and the noise was GONE. The steering-deflection-at-low-speeds was also gone, but I think that was due to the bubble on the right front tire.

Tips:

1. The winning combination for the big nut on the outer CV joint was a 1/2" breaker bar with about a 4 foot piece of 1.5" galvanized pipe over it, and an accomplice to step on the brakes while initially loosening the nut. (1.2 meters of 38 mm pipe.) Without them stepping on the brakes, I think you're applying a lot of torque to the park pawl in the transmission. Make sure to use a punch/drift to un-stake the collar on the nut from the groove in the end of the axle, first.

2. If you have to get a CV axle out, it's absolutely worth renting the slide hammer and giant C-shaped claw for it from the auto parts store. It turns an hour of screwing around with screwdrivers and pry-bars into a few minutes of increasingly intense action on the slide hammer.

I got my slide hammer and claw from O'Reilly. Due to clearances, you might have to slip the claw over the tapered end of the inner CV joint first, and then thread the slide hammer into the claw. If you plan to re-use the axle, make really, really, really sure that the claw is bearing on the thick cast metal inner CV joint housing, and not on the stamped sheet-metal "dust seal" that is right next to the transmission - if not, you'll bend the dust seal. If you've already decided the axle is junk, then just wail on it with abandon.

Also, it's worthwhile to open up the slide hammer case at the store, and inspect the threads on the end. The nature of the beast is that these threads get beat up as people use the hammer. If you can't get the "claw" threaded on to the hammer far enough, politely decline to rent that hammer, and try another car parts store.

3. The Chinese ball joints from the car-parts store come with new locknuts, but the hex part is not nearly as tall as the factory Toyota nuts, and the hex can almost handle the specified installation torque. If you need a new ball joint, it's probably worthwhile to buy some full-height nuts of the appropriate size, and use Loctite, rather than use the Chinese nuts. I also re-used the "class 11T" Toyota bolt for the ball joint, as I trusted it more than the black phosphate Chinese bolt that came with the ball joint.

4. General tires are junk, don't buy them.

I am not affiliated with any companies mentioned.