ABS kicking in on dry pavement

[ponkotsu]

This is an '05 Aviator. Today my ABS started kicking in under low brake force on dry pavement. It was pretty violent and erratic. Made it difficult to stop. Did it about 3 times and then stopped.

My first thought is a bad wheel speed sensor. This might correlate with another issue I have. Often when stopping at high speed I get significant steering wheel wobble. The front end is all brand new parts and properly aligned, so it's not suspension related. And I've measured the rotors and they are parallel well within spec. Tires are in decent shape and recently balanced.

Wheels don't appear to have any play in them like a bad bearing, but I've been fooled by that before where they feel tight only to find out they are fried.

If not the wheel speed sensor, I'm not sure what it could be other than a bad connection.

I found hubs super cheap on Amazon so I ordered them as insurance until I figure it out. Anyone think this diagnosis is correct?

 

[Number4]

A bad hub could certainly be the issue. However, here is my suggestion. Part out your car. I'll take the front knuckles and the backup sensor assembly.
I know it can be hard to let go sometimes, but this simply works out best for me.
Before throwing parts at it though, might have the ABS system properly diagnosed.

 

[Albino 94LTD]

I experienced the same and it was a bad hub assembly.

The sensor tolerance is pretty tight so it doesn't take much play to get out of range.

 

[ponkotsu]

I experienced the same and it was a bad hub assembly.

The sensor tolerance is pretty tight so it doesn't take much play to get out of range.

After doing some research I think this is a pretty common problem. I bet they are original just like everything else was on this truck, so are due for replacement.

 

[ponkotsu]

A bad hub could certainly be the issue. However, here is my suggestion. Part out your car. I'll take the front knuckles and the backup sensor assembly.
I know it can be hard to let go sometimes, but this simply works out best for me.
Before throwing parts at it though, might have the ABS system properly diagnosed.

Absolutely brilliant idea. I'll throw away an $8k vehicle because a $100 part is worn out. Brilliant!

 

[Number4]

Like I said, it would work out for me.

 

[Albino 94LTD]

After doing some research I think this is a pretty common problem. I bet they are original just like everything else was on this truck, so are due for replacement.

Do you by chance hear any grinding like grit against the rotor? That was my big indicator.

 

[ponkotsu]

Do you by chance hear any grinding like grit against the rotor? That was my big indicator.

Nothing I hear when I'm driving, but when spinning the wheel a little by hand I can feel and hear it hitting hard on half the revolution. I got new OEM Motorcraft hubs on Amazon for $39each. with free shipping. I think it was a typo, because after I ordered the price went up to $149. So this is a no-brainer, the Aviator is getting new hubs this weekend.

 

[ponkotsu]

This project snowballed a bit. Changed out both front hubs with new Motorcraft. I mentioned earlier that I got them super cheap. Seriously, I only baid $80 for the pair including shipping. They are Timken branded in Motorcraft box so I know I got the the good stuff. After changing the hubs out, I still had some vibration when braking. I never suspected the brakes because they were just redone right before I bought it last year. Freshly cut rotors and new pads. Well, I guess I should have checked. Brought the rotors in to get the resurfaced. The mechanic measured them and said they were .008" out of parallel. I checked for myself and they were terrible. He said he'd never seen such a bad job of cutting a rotor. So looks like whoever did the brake job did a total hack job. I bought from a used car lot so probably the did it. I'm guessing the bad rotor is what was causing the ABS issue and maybe damaged the hub. The hubs felt super tight so I kept them for spares. New rotors, pads and hubs, and the Aviator is smooth. Not much left to fix!