Low Grumbling Noise When Braking in 4x4

[brian2sun]

I noticed that when I'm in 4x4 (hi or lo) and going <10 mph, when I'm on the brakes there's a grumbling noise up front somewhere. It's not very loud, but I never noticed it before this winter. It goes away as soon as I let off the brakes and it will not happen in 2wd.

I pulled my ABS fuse so it isn't that. My CVs, diff bearings, rotors, and pads are all less than a year old and I don't have any indication of bad wheel bearings. Any thoughts? ADD + brakes at the same time = vacuum thing maybe? Or maybe it's normal and I just never noticed it before now? It's pretty low in tone. hmmm. :shrug:

 

[Toy4ever]

I had the same thing happened this weekend when i was braking. The only time it would happen is when i was facing downhill and would brake on ice. Someone told me its a normal sound regarding your ABS but it was just an opinion so i don't know.

 

[Lignum]

Wouldn't you feet the pedal vibrate if it was ABS?

 

[Toy4ever]

I am by all means not the expert so i couldn't answer this question correctly. But that's what happened to me and like i said the strange part was it only happened on the ice.

 

[brian2sun]

Yes, the pedal should pulsate if it is just the ABS making the noise on Toy4ever's and that's totally normal on ice or other loose or slick surfaces. But, since I pulled my ABS fuse a long time ago, ABS is definitely not causing my noise.

Any other ideas anyone? Maybe this is normal cuz it doesn't sound like it's causing damage, it's just more of a soft grumbling noise. It really sounds like the pads are just making contact with the rotors, but then why doesn't it do it in 2WD? Possibly the brakes are working harder since there's power going to the wheels and they have to fight against that - unlike in 2WD when it's just rolling and not under power?

 

[quicksilvr]

Yes, the pedal should pulsate if it is just the ABS making the noise on Toy4ever's and that's totally normal on ice or other loose or slick surfaces. But, since I pulled my ABS fuse a long time ago, ABS is definitely not causing my noise.

Any other ideas anyone? Maybe this is normal cuz it doesn't sound like it's causing damage, it's just more of a soft grumbling noise. It really sounds like the pads are just making contact with the rotors, but then why doesn't it do it in 2WD? Possibly the brakes are working harder since there's power going to the wheels and they have to fight against that - unlike in 2WD when it's just rolling and not under power?

There is virtually no difference in how hard the brakes have to work in 2wd and 4wd. If it's not doing it in 2wd, it's not the brakes.

I don't really have any good idea's for you though, sorry. :shrug:

 

[Mr. Leary]

I noticed that when I'm in 4x4 (hi or lo) and going <10 mph, when I'm on the brakes there's a grumbling noise up front somewhere. It's not very loud, but I never noticed it before this winter. It goes away as soon as I let off the brakes and it will not happen in 2wd.

I pulled my ABS fuse so it isn't that. My CVs, diff bearings, rotors, and pads are all less than a year old and I don't have any indication of bad wheel bearings. Any thoughts? ADD + brakes at the same time = vacuum thing maybe? Or maybe it's normal and I just never noticed it before now? It's pretty low in tone. hmmm. :shrug:

Obvious stuff, so I apologize ahead of time.

Check CV boots.
Check front drive shaft.
Check front diff fluid for shavings.

If you are stumped... Put the whole truck up on jack stands and put it in 4wd and let the wheels spin... get under it and poke around, might jump right out at you. Just be careful, a mistake when performing this procedure could get somebody hurt or cause a lot of damage to your truck, property, etc. Always safer to have somebody in the truck ready to hit the brakes if it comes off the stands.

 

[brian2sun]

Thanks for the replies, I'm planning on changing the oil in the diffs and t-case soon, so I'll probably just move that to this this week and see. CV axles are <1 year old and the boots look fresh and the front driveshaft seems nice and tight. My diffs are still under warranty for 2+ more years (when I got my gears installed) so if I find anything funky, I'll take it back and have them re-do everything for free.