Hi all - I have spent several hours searching previous posts and couldn't find any reference to this problem, so here it is:
I have a early 99 SD PSD 4WD Supercab with 196k miles. All new rotors and pads about 55k miles ago. It has developed an intermittent vibration while braking that (when it does occur) only happens between about 43 to 35 mph. It feels like it is coming from the rear of the truck as there is no shake in the steering wheel. When it is bad it will bounce the coffee out of my cup and when it is good it completely disappears. The only other noticeable symptom is that when it is bad, during the final part of a stop, from say 3-4mph to zero, there is a noticeable pulse to the braking. When it is good this pulsing is also gone. I have taken it in to my mechanic a couple of times and per Murphy's law, he couldn't duplicate the vibration. I have also tried putting it in neutral during braking to no effect. This has been going on for quite a while and seems to be getting worse which is what prompted this post. Any ideas or help you could give me will be greatly appreciated. Thanks,
Sedona Bob

 

There are a number of things that can cause a problem like this. I'd start by cleaning and lubricating you caliper slide pins.

Also, brakes can be totally worn out way before you get 55k on them.

 

Redford - Thanks for the quick response. I apologize for taking so long to get back to you but it has not been easy to find the time to follow up on your suggestions. I have checked all of the caliper slides and they all move very easily, are very clean, and seem to have plenty of grease. Checked the pads and decided to replace the front ones as they were down to about 25%. Rear pads are at about 80% so I didn't replace them. All the rotors appear fine with no strange wear marks. Put the front rotors on a trueing machine to scuff them up for the new pads and they have no wobble. Put it all back together and the problem actually seems slightly worse and occurs more frequently. Do you have any other ideas?

 

Steering stabilizer maybe? Just take the bolt loose on one end and check for resistance.

 

If the vibration only exists while braking it's most obvious the braking system is at fault. You said you trued up the front rotors but assumed the rears "looked" good. I would test them as well. It is funny though that it doesn't happen at a highway speeds. Even slightly out of round rotors will generally be more pronounced at higher speeds.

 

bayou bareataria - thanks for the idea. I will try to check the steering stabilizer tomorrow or this coming weekend and let you know.

DAVE67FD - checking the rear rotors will probably have to wait until sometime next week when I can get it into the shop. The limited speed range where the problem exists has baffled me also. When braking from 75 to 0, there is really no vibration at all until I get below 45mph, then it disappears again under 35, although I have noticed an almost negligible vibration under 35 in the last few days, so I think it is slowly getting worse. There is still the pulsing from 5mph to 0, which also seems worse in the past few days.

 

I agree with DAVE67FD. There is no way you can tell if a rotor is causing the problem by looking at it. Warping the rotor less than 1/100 of an inch can cause issues.

Most shops will just turn the rotor on a lathe and install new pads. I don't like to do this because you come out of it with a thinner rotor, which in theory will warp easier next time.

 

There seems to be a very common issue here with these larger trucks and vibrations when braking. I had this very issue with my 2000 F250. There is alot of heat and friction on the brake system, trying to stop these big beasts. Rotors can get out of round pretty quick and easy. I replaced my rotors with a higher end ones and ran them for a few weeks. Then I replaced my pads after a few wks with the rotors. That way I would have nice new pads on the new rotors, to give it a smooth beginning. As always, lube the mess out of everything and make sure everything slides easy. Good luck bra.

 

other things to check, pads can get glazed if they have been hot, they can then leave deposits on the rotor which will cause that symptom. a soaking with brake cleaner and a scuffing with 60grit should remove deposits. the most common cause of brake vibration or pulsation on a non warped rotor is improper wheel torque. if a wheel is not torqued properly and in sequence it can stress the rotor just enough to make it act out of round.

 

Just a question, maybe i missed it, but is the vibration/pulsation in the rear of the truck like the bed is bouncing up and down slightly? OR can you also feel it in your foot while you are braking?

I am wondering if you might have 2 issues going on. Maybe you are suffering from slightly warped rear rotors, and you are experiencing the "Superduty Hop" which occurs, mostly in long bed CC, but has happened in shorter trucks too where at about 42-50 or so MPH the bed bounces at about 9Hz (reason unknown). Just a crazy idea. Maybe i am off base.

 

Thanks again to all for some great ideas and places to look for my problem, which seems to still be getting worse by the day.

Redford & Scottzj - I am really going to try to find the time to get it into a good mechanic next week and have all of the rotors checked. These rotors have never been turned so if they are out of true I may try that just to see if that fixes the vibration. I do agree that thinner rotors will warp easier but if turning them fixes the vibration at least I will know what the problem is(was).

02mudbug - If I get the time this weekend I will try your suggestion for knocking off the glaze and see what happens. As far as wheel torque possibly causing the problem, I will check that again, but my torque wrench only goes up to 150 ft-lbs and I have been reading in this forum that the correct setting is 165. Maybe I don't quite understand this aspect but it would seem to me that as long as they are torqued in the proper sequence and are all equal this 15 ft-lb difference would not cause warping. Please let me know if this is not true.

Gunnerdog - The vibration seems to be mainly in the rear of the truck, although in the last couple of days I am noticing it more and more in the pedal and even a tiny bit in the steering wheel. I don't think I have the superduty hop as everything I have read about that seems to indicate it occurs at certain speeds, with or without braking being involved. My problem only happens when braking.

Thanks again for everyone's help and as soon as I have some new information on this (hopefully next week) I will let you all know what I discover.

 

When i had issues with the calipers hanging up on me (just replaced my 3rd caliper at about 80k) and severe heating on two of them (ironically both rears) i had slight vibrations only when they were hanging up.

When the rear left caliper went (50k) they replaced rotor and pads (got severely overheated) as well and pads on the opposite to keep them matched. Front left went and only replaced caliper (no heating). Rear right caliper went and they turned rotor and deglazed pads. Have not replaced front pads yet at 80k with still plenty of meat.

 

Another thing to check, I run into this a lot on my trucks; with these heavy duty tires with the high pressure if the shocks are weak the tires will cavitate [hop] at certain speeds especially if you keep 80 p.s.i. in them. Do the tires show uneven wear? That can be a sign of wheel hop. I always replace the shocks as soon as I buy a truck even new with kyb's or bilstiens because I keep 80 p.s.i. all the time.

 

OK - truck went into the shop today. Replaced the rear rotors, turned the front rotors (left was much worse than right), checked ball joints(ok) and tie rods(also ok), checked calipers again(still ok). Brakes are working great right now with no vibration at all (almost forgot what that feels like). I will post again in a couple of weeks and let everyone know if the vibration stays away. Thanks again for all the great advice. You guys rock!

Bob