I have a 2001 V6 F-150 with 160,00 miles. I am trying to track down a vibration that is most noticeable when braking. It seems to shake most violently when braking from high speeds. It feels like maybe the torque converter is not unlocking properly because the the truck seems to shake more during down shifting.

On the other hand, the power brake booster make a "creaking" noise when the brake pedal is pressed. Other times, it will not make the noise and the pedal is not as spongy. The shaking is significantly less when the booster sounds creaky and is spongy. Is it possible for a faulty diaphragm within the booster could cause the shaking by pulling an inconsistent amount of vacuum from the engine? That idea seems a bit like a stretch, but I have been grinding this out in my head for too long.

I just replaced to tire, might have been out of round. I checked the calipers, greased the slide bolts. They seem fine. Pads are worn a tad bit uneven, but nothing eye popping. Truck also has new plugs, fixed isolator bolt issue, replaced egr valve, dpfe, pcv. Mostly accomplished from all the awesome info on this site.

Any ideas, I think I can see the forest for the trees at the moment.
Thanks in advance.

 

Did you spin your wheels when they were in the air, you could have warped rotors. If you spin your wheels and they seem to be free but garb in a spot then that would be your warp.

 

ok, here is a bit of an update.

I replaced the brake booster and pads this weekend. No change in the shaking during braking. Had my friend pump the brake pedal while I listened underneath the hood to try and track down the creaking noise that comes from the booster/mc area. The noise definitely seems to originate right at the connection between the booster/mc. I also checked the calipers, none seemed to be damaged or sticking.

So at this point I am thinking maddoughboy is right and it is my rotors? Only thing is that, although currently the shaking is consistent, there are intermittent times when there will be no shaking. If the rotors are warped, I would think that the symptoms I am experiencing would be every single time I hit the brakes? Starting to think it is worth a 100.00 diagnosis by a shop and then I can take over the labor after that.

 

It's the rotors-mine was shaking the same way you discribed. The high speed shake is worse b/c the rotors get hotter. Mine would also sometimes be smooth as glass,other times shake like crazy.

Save the $100 and put it towards new rotors.
Or you could send it to me! ha ha!

 

Thanks to those who gave their opinions (and all the board members for that matter). I ended up taking the truck to a shop, they gave free diagnosis and concluded that is was in fact my rotors. I let them machine my rotors and replace the bearings for 180.00 Thought about doing it myself, but with my two jobs I have been left fairly worn out. So in time alone, i feel it was worth it.

To conclude,

Truck stops smooth as glass now. I feel as if the shaking was 90 % rotors, and 10% still remains during shifts. I can deal with that for a 160,000 mile truck.

Cheers