But not every time,


More so when braking hard & less with light applications but does not occur every time.


Found the thread abt wheel torq & chkd out ok & still have 245's.


Quick punch of pedal tho will produce the shake(whole truck) every time & pedal gets closer to the floor.


Fluid is only abt one hair low.


Have heard abt this prob before but my search with brake hop & brake shake didn't find the culprit. Ruled out rotors sense sometimes it brakes as smooth as ever?


Had a like prob with Suburban at 110k mi but it was all the time & cured it with a hefty(very expensive) set of rotors.


Hate togo dealer away from home but need a fix asap.


thanx, gben

Don't rule out Rotors because it is intermitant. I have a 99 Jeep grand cherokee that warps rotors every 8000 miles, and when it does the vibration happens sometimes, sometimes not. Think it has to do with where the warp is on each side of the front relative to each other. The best way to tell is put a dial indicator on them and see what the run out is. You may be able to detect some warping just by raising the wheel and turning the tire and feeling for even drag all the way around the rotation, but not as good as a dial indicator. Edited by: srode

I agrees I think rotors are the culprit too. They are warping and
hotspoting and are fine cool and get worse when they heat up. My wife
has a 2000 Cherokee that the front rotor act the same way and I need to
change them sometime before it get worse (presently it only does it on
hard stops from high speed)
Edited by: snoman

I would concurr, definitely a rotor warping issue. Have them surfaced and should fix the problem. Check your pads for cracking..Vibration from warped rotors will start and propagate cracks leading to pieces potentially falling out.

It has been my experiance the warped rotors are best replaced as
turning them can lead to thickness variations in the surface that can
lead to future hot spotting and warping.

Snoman,


Great point.


Sadly these rotors are not cheap units. I would find out how bad they are and if significant material had to be turned out of them, then new ones are the best bet to eliminating it all together.

If your going to renew or replace the rotors, do yourself a favor and replace the pads as well. Don't forget brakes need to be broken in as well. No quick stops or trailering until the pads bed in. http://www.dieselplace.com/forum/smileys/smiley2.gif

Snoman,


Great point.


Sadly these rotors are not cheap units. I would find out how bad
they are and if significant material had to be turned out of them, then
new ones are the best bet to eliminating it all together.



ALso softer pads with less metalic content tend to less furture
problems as well. Yes the pads wear a bit quicker when they are softer
but the are easier on rotors and lessen hotspoting and well. I use them
all the time as it is cheaper and easier to change pads more often than
replacing rotor before pads are worn out.

hate to go against the grain but i highly doubt its a warped rotor. the rotors on these trucks are HUGE, there twice as thick as a rotor on a cherokee, you'd have to be doing some serious braking to warp these suckers. does the pedal pulse at all to match the viberation? if not, it aint the rotors. now, my truck is currently in the shop, they replaced the idler arm and intermediate shaft, both went bad. guess what happens when these go bad.... truck shakes and vibrates bad under braking, 'but not every time'. i would have your front suspension checked out, if you can put it on an alignment rack and push and pull one of the front tires, if it moves but the other one doesnt it's likely the idler arm or something in the steering box (intermediate shaft) good luck and keep us posted.

Thick or thin they can warp and or hot spot which can cause brake
shudder and shake. Todays hard pad do not help matter either as with a
couple of very hard stops or brake heatings you can hotspot the rotot
which leave different drag coeffiecents accross its surface which make hots spots worse and can lead to warping. It may take more to warp one but you still can none the same.

Thanx Guys,


I dug the Survice Mgr out this afternoon here at Murphy NC(Jacky Jones GMC) & he said, NOTHING. Yes he talked a lot but would not even guess. He did say, could be several things & he repeated that verse at least half a dozen times. He even got me saying it.


The guy got so carried away with the Cat filter & the Stanadyne setup under the frame he could not concentrate on nothing else. They were covered up & couldn't get a service bay open to lift it on a rack. But that didn't keep him & his sidekick from under the truck.


Made me promise to come back in the morning for diagnosis which I wouldn't be charged for! But the complete brake job which includes rotors which he said prob isn't needed could run over $700! I'm guessing that they will offer to turn the rotors for abt half that? Rotor prices there are $90 & non oem upto $140 each ie, ouch!


But before I goto J Jones tomorrow I will go up the road to my friend who sold me some Cooper tires couple years ago. Talked to him tonite & sense he knows trucks whatever he says will pretty much rule.


No there is no feedback thru the pedal but sense this was brought up we did have good bit of feedback with the 99 Tahoe before the rotors were turned at abt 35k mi.


Thnx agn Guys & I'll be back as time permits.Edited by: Gbenzx

Well Guys Today did not solve the prob,


But today did not have the problem. The pit crew at GMC said the warp was so slight rotors were not worth turning.


The thing I didn't mention sense I thot it wasn't relative was that the bed was loaded with abt 2500lbs of tools & other stuff & the Cherokee was being towed. But today with abt 6-700lbs in the bed & no tow we could not reproduce the prob although we tried til tired.


My friend at the tire/grocery store up the way has had a minor shake with his when pulling his big boat. He solved it by adjusting the ball lock mechanism on the boat trailer so that there is no slack between truck & trailer. I will try to see if this can be done on my towbar before we tow back to fla.


We did chk tierods, steering, idler & everything under the front. Yes there is wear but very minute & not prob prone yet & tires are wearing straight as they should be.


From high speed & water stops I've always been careful not to hold high pressure against the rotors while cooling. I will usually stop a few feet back in order to move ahead in small increments while cooling but then again %@*#, sometimes others have to drive the truck too.


Just have to see if this reappears after the ball lock is fixed, duuhh maybe the jeep trying to run into my truck!


Thanx Guys, Gben

If there is a slight warp when rotors are cold cause by stress in the
rotor, it can get a lot worse when they heat up as your past problem
supports. Turning will not fix this kind or warpage, only replacement
will.

I have the same intermitent problem on my truck and I am almost at the 80,000mi mark. It would not surprise me that it would be either the rotors or the the steering components have loosend up a bit. I will have to brake soon I think so I will have the front end inspected as well. No uneven tire wear though...

Chevy,


Just wondering, have you had any brakework before now & do you do any heavy hauling/towing?


My friend Hamby says that heavy haulers they are seeing will need brakework 55-65k mi & light duty are coming in around 80k mi or more.


We have to consider ours a heavy sense every time it's cranked up generally it is hooked to at least something & sometimes heavy something. I must concede that we do have a warp condition on one of the four rotors tested but will not turn them just yet.


Also I have not been apt abt using towmode when loaded except when in the mtn country. I've got todo better after discussing it with aDmaxer last nite that hauls tractors to auctions. He has 78k mi on his with no brakework yet!


Also just installed Hypertech for mileage & went abt 40 or so more miles on usual 26gal. but will see for sure after 2-3 tankfills.http://www.dieselplace.com/forum/smileys/smiley4.gif


Thanx Guys, Gben

My 2000 K3500 needed a front brake job after only 25,000 miles. It is
used a lot in winter and caried a heavt salt load and a plow too. Never
had any shudder/shake problems with it though.

Our HDs have very large brakes and on my truck don't even work up a sweat. When I was doing front end and brake work I would occasionally find a caliper that was not floating properly. This was the number one cause of an intermittent shimmy. The worn front end parts would really aggravate the problem. Improperly torqued wheels can warp rotors also but I don't know about our HDs. I do know that as little as .007 total axial run out will cause a problem. Rotors are easily checked with a dial indicator. Later! Frank

I never had a lack of brakes at any time with any load as there was
always brake left over but for some reason they did not last very long
and I am not hard on brakes either

Thanx Guys,


Frank, are you sure? A sticking caliper was mentioned by one of the mechs at the GMC shop & the Ser Mgr replied, not on an hd truck, as a ques & he said no. May need to rerun this one. But how could one know far enough in advance to save the rotor?


Now let's see here anyone sell caliper guages? How abt those stink bombs like in the big rigs for bearings & such?


One more thing tho I am so thankful we did not buy a furd 6.0my = nuff said!


Gben

I don't do a much of any consistent towing and I drive a lot of highway miles. The brake still have plenty of pad on them as well. I am thinking of changing them soon, just because of the mileage I have on the truck...