Brake Issues

[bruce69camaro]

I have a 2000 Sierra 1500 4 x 4, I'm having some brake issues and not sure what the problem is?

I have been hearing a humming noise coming from up front, I was thinking the transfer case was getting low on fluid because it has a small seal leak.

The noise only happens after I have been driving the truck for 10 minutes at highway speeds. Then after leaving work, the noise again returns after driving it for 10 minutes.

I took it to a shop and they found both front calipers were locked up and he suggested replacing both calipers, hoses and pads, which he did.

After the work was done, the noise is still there, but quieter.

The one thing I have noticed is, at first the brake pedal is a little spongey, but after driving it for those 10 minutes, the brake pedal becomes solid.

I also start to feel a slight virbation.

A friend mentioned that maybe some pressure was being kept in the line?

Any thoughts?

Thank you

[davester]

make sure the transfer case doesn't run low, as it'll kill the bits inside quick enough when it does.  And also check that the pump rub hole hasn't happened, as that'll also wind up dumping all the fluid out (if you haven't applied a pump rub fix in the past).

[DeplorableACE]

On 5/18/2020 at 12:56 PM, davester said:

make sure the transfer case doesn't run low, as it'll kill the bits inside quick enough when it does.  And also check that the pump rub hole hasn't happened, as that'll also wind up dumping all the fluid out (if you haven't applied a pump rub fix in the past).

I have same truck as OP, no brake issues, but whats the pump rub hole and how do I check to see if I have it? My truck has 180k miles.

[davester]

4 hours ago, DeplorableACE said:

I have same truck as OP, no brake issues, but whats the pump rub hole and how do I check to see if I have it? My truck has 180k miles.

google "gm pump rub" lots of info about the problem, and how to fix it, the fixes varying in cost [rear case half made of a different metal, or a billet pump or a pressed-metal plate (what I've used)].  It's a weekend project  (could do it in one day if you really want to), mostly one person job except for getting the transfer case in/out of the truck (even with a transmission jack on a driveway/garage, you really need a second person to help rotate/shift the transfer case to get it in place).