No clunking until replaced front end brake pads and rotors. Pontiac Montana 2002 not a FWD. I'm not 100% sure but I also believe I can feel a vibration on steering wheel coming from front.

It may be a loose suspension part (struts, sway bar, etc.), but I would take a close look at the brake calipers - the pads inside and outside of the rotors are slightly different and must be installed correctly, and any pad vibration clips must also be installed correctly. Also make sure the axle nut and wheel lug nuts are torqued correctly.

Is the run out on the brake rotors within specs and are the brake pads fitted tightly in their mounts and high temp synthetic brake lube been applied behind each brake pad?
Also the wheel nut torque needs to be correct tightness so the rotor does not move on the wheel studs.

will try to help. when front wheels shake while applying brakes and you can feel shake in steering wheel, front brakes and rotors need replacement.rotors are warped,if you replace front brake pads, it will return[shaking when you apply brakes] suggest that you replace front rotors[both] replace [both]front brake pads. cost? i would charge [brake pads cost $55.00] labor,$60.00] total $115.00 thank you for choosing fixya.com

You know this is hard to believe. Brake pads should go at least 40,000 even on the front. Calipers should last about 10 to 12 years. That's my record for 46 years running.I wish I had the vehicle and time to review this with you. Start from 05 and discribe every brake issues and EXACTLY what was done and why/

Not likely any bearings...
Most likely the brake pads are worn down to the metal rivets that hold the braking material to the shoes (or pads).

The rivets have made a "rut or ridge" in the brake rotor or the brake drum.

If the sound is in the back, then the brake shoes must be replaced and at least one drum has to be replaced.

If the sound is in the front, then the brake pads must be replaced and at least one rotor has to be replaced. The front rotors can be viewed easily with a flashlight, shining through the wheel.

The read drums may be very difficult to remove; patience.... and care...

have wheel speed sensors checke

When the shuddering starts pull off the road way get out and feel the rotors on all 4 wheels. If any are very hot you have a caliper piston hanging and holding the brake pad too tight against the rotor.

Good! You bled the master cyl. before installation! The proper order of bleeding the lines, is to start with the wheel the greatest distance from the master cylinder. Then work your way to the next greatest distance, and last, the closest wheel. Make sure all air is removed from the lines before you proceed to the next wheel, and frequently check the master cyl. level, because, as I'm sure you know, if you **** in air at the master, you have to start all over again. I'm assuming you don't have a power bleeder, so with a helper do this with car running (make sure it's on safety stands and not going to fall on you!) Pump pedal 3 times, no need to mash the pedal into the floor, just 3 pumps 1/2 way down, hold 3rd pump at half way down level while bleeder is opened, when flow is about to stop at bleeder, close bleeder and repeat til no evidence of any air. Let me know how it goes and if you need any help.

Air in the brake system bleed the air out

If you can feel it in the brake peddle when you push on it, then your brake rotors are warped. Putting new pads and rotors in will solve this. Is caused by braking too hard (driving really fast to a stop sign and stopping in the last few feet). I have heard a few times that some people upgrade to a better brake when they increase wheel size, but I do not think that is a problem in you case.