Strange ABS issues in 05 Tundra

I'm having a problem with the ABS in my 05 4.7. In dry or wet it will lock up the fronts...assuming the pump is on during this as when I let off the brakes I hear/feel the abs pump for a brief moment. In snow/ice the truck locks up the rears with the abs pump audibly on. No lights on in the dash - other than tire pressure from dead sensors.

Brakes are in great condition, fluid flushed less than a year ago.

Any help is much appreciated.

 

Probable have a leaking rear seal. The gear oil has leaked onto the rear brake shoes and they are doing little braking. Pretty common.

I'm not sure if your truck has pads or shoes, but I thought it should be mentioned.

 

Front discs and rear drums.
Rear wheel cylinders are not leaking.
Even if the rear shoes were soaked in brake fluid, shouldn't the abs prevent a front lock-up? When I say lock up I don't mean the normal little chirps you get with an abs stop, I mean it is locked up and will stay locked up until I let my foot off of the brake.

 

I see now.

You may have a bad wheel speed sensor.

You don't have any CEL lit on the dash?

 

No lights on the dash - other than the tire pressure from the dead sensors, but that is being fixed because the light has won the battle of wits over my stubbornness to open the wallet.

Is why this is a 'strange' abs problem. Any time the abs fails to the point of locking tires up, the cluster should be lit up like a christmas tree.

 

Either a bad wheel speed sensor or the tone ring has debris/damage.
That typically is what will cause this. Logging it in a scan tool may tell the story

 

Does the abs light come on when you turn the key on?

Did the abs ever work since you have owned it?

Wondering if previous owner disabled it because abs sucks.

 

It did work, and not too long ago. I bought the truck in 3/2019 and never buy a used car without first cycling the abs multiple times - for exactly the reason you mention

It wouldn't bother me all that much but if my wife ever gets stuck in the snow/rain with the truck....well....I like this truck.

I'll be checking the wheel speed sensors and rings...hoping it is dirt or debris - with the thought that a bad sensor would light up my abs light.

 

Sounds like a leaking rear axle seal soaking your rear brake drums and shoes in gear oil (like Kodittion said) not a leaking rear wheel cylinder like you referenced and/or out of adjustment rear brakes.

 

Aw hell...

 

Was that already broke or did it break pulling on it??

 

I broke it all of the way, but pretty darn sure it was already messed up.

 

Denso. Thanks previous owner.

 

Opinions vary but Denso for our Tundras have more fans than not. I feel confident the engineers did not take into account how bad some of these trucks suck rust wise and that one is definitely knurly lookin.

 

When one of my rear wheel sensors stopped reading it turned on the ABS light. If you have no light on I would still pull the rear drums and check the condition. I still think you have more issues.

 

ABS light went on when sensor broke...so sensor may have been ok? Replaced, light out. Tone ring looked brand new in there.
Denso may be factory sensor, I thought it was autozone/advance auto hogwash, my mistake. Some suspension components are rusty but the body & frame are perfect. Toyota replaced the frame in 10/2015.

Slammed brakes on a gravel road. Still seems to lock up (alternating sides it seemed) for .5-1 second.
Scan tool shows all wheel speed sensors working properly...
By all measure ABS appears to 'work' just very slowly and sluggishly.

If your ABS is working properly - does it ever lock up a wheel for longer than a chirp, in any conditions? I don't want to accept that the abs in these trucks are just that bad...

 

You say the ABS worked fine when you bought the truck a year ago in 3/19. Have you removed the brake drums since this problem started and checked the brake shoes and hardware? Brake condition will affect ABS operation and your going in circles if you don't visually confirm your brakes are adjusted properly and in good shape.