I’m getting some pretty bad shaking when braking light to moderate amounts. Here’s what I’ve done so far that hasn’t fixed it:

- New front rotors, calipers and pads
- Replaced rear axle with low miles used one. Used those drums but replaced the wheel cylinders, shoes and brake hardware.
- New radius arm bushings
- Dynamic balanced wheels with weights on the outside.
- I assume not related but replaced the motor and trans mounts too.

The new front brakes seemed to fix it for a bit, but I’ve got maybe 1000 miles on them now and the issue is back.

It could be that the issue never fully went away. Hard to tell since most of my mileage is a quick 10min drive to work without much highway, where it’s most noticeable.

I did a 600mi trip this past weekend and the shaking was very apparent.

What seems a little odd is that the shaking will build if I keep consistent brake pressure, like it’s hitting a resonance and continues to elevate the severity.

I’d be astonished if I already warped the new rotors since I barely haul more than a few hundred lbs of dirt bike and gear.

 

Outside of my sandbox, but suggest going through the steering components, looking for looseness and slop, including the PS box mounts flexing on the frame.

Had a '74 Mercury Capri (the sexy European) with similar issues, traced to the rubber mounts isolating the front axle-mounted rack-n-pinion that became spongy due to the notorious 2.8L V6 front main oil seal leak onto them - thing would about wobble itself off the road during a normal stop, tracked straight and true during a romp-n-stomp (hard) stop. Replaced the mounts (Ford part number D0RY-5484-A and D0RY-5484-B, ingrained in my brain because replacing them numerous times as needed was easier than fixing the oil seal leak), and all was good again.

 

It would seem to me if the shaking is happening while your braking, not as you are driving normally, it has to do with your braking system. You may want to go over your braking system again. I had some shaking/pulsating issues once after I did my front brakes. Found that the company that turned my rotors probably didn't do a good job. Put new rotors on and went away. Also make sure all the grease that goes into doing a disc brake job is done properly. Usually that will cause uneven wear of the pads. If you used the old drums and didn't have them turned, that could be an issue.

You didn't mention what year your truck is, so I am advising you as if you have an OBS like mine. The front disc brakes are a much better braking system than the drums in back. I actually set my truck up so that the front brakes do most all the work stopping with some assistance from the rear. I do not like it the other way around. The plus for me is that I feel more in control when I am braking, the minus is that I do a greater number of front brake jobs.

 

A dial indicator on the front rotors to see if they are warped again
Test drive and apply the E brake to check the rear drums for out of round
Check for front rotor thickness variation with a micrometer
Good luck

 

I have a 1990 F150 4x4 that I have owned since new. I've recently gone through the whole suspension and most of the drivetrain. Despite new rotors, wheel and axle bearings, suspension bushings, etc, I had a terrible shake when braking. I put a dial indicator on the rotors, and they were very true, like within .001".

One day on the interstate, I tapped the brakes with the cruise control on and realized that it did not cut off the cruise. I then checked and found out I didn't have brake lights. I got out the wiring diagrams and meter, and found a blown fuse, the one supplying power to the brake switch. I replaced it.

My next trip down the road, I was really surprised when the truck stopped really smooth, no shaking. The fuse had fixed the shaking.

The brake switch sends a signal to the RABS module when the brakes are applied. Without digging deeper into the operation of the RABS, I can only assume that applying the brakes without the module receiving a signal was causing it to pulse the brakes in some erratic manner. All I know for sure is that restoring the signal fixed the shaking.

It's worth a look.

 

Un commanded ABS operation is a big problem when it happens
We had a 96 Taurus in, that the guy had adjusted his master cylinder pushrod out a bit because he thought he had a low brake pedal (new car at the time)
Damn thing was applying the brake when the fluid warmed up going freeway speed on its own (not ABS related though)
Shimmied like a death wobble, then if you hit the brakes, it would go away.
Took quite a while to figure that one out
Moral of the story: Do not adjust that booster pushrod without using the special tool