Pontiac Grand Prix Forums : Grandprix

It started about a week ago.... When your going down the road at around 25-30 it begins this thumping noise and the faster you go over 30 it gets a more rapid thump. but when u jerk the wheel the noise seems to go away then when ur going striaght again it begins the thump again??? alignment seems great... im leaning towards the breaks and rotors sound about right or no? sometimes when its thumping the break pedal may pulse. Im kinda lost

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hogan 3inch DP u bend delete ,180*tstat, autolite 104s, LED interior, 4" FWI, 2000watt system, bullitt rims, zzp pistons, pems, alt rewire, thrush muffs, 3.4 zzp mps, transgo shift kit, triple edge performance trans. autometer triple pod :SOON: urlosn HPT PCM tune, HEADERS, 1.9's

are your tires out of balance?
checked your halfshafts?

busted spring possibly?

if you drive on 31 between bull valley and crystal lake, id check the springs.

uhhh..wheel bearing?

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98 XGT - sold
06 impreza 2.5i 5 speed - stock, slow, and awesome

I've done some horrible crimes against cars, and i'm just gonna guess a scenario here because this is how I did it... One of the front wheels is out of balance, or a shaft is vibrating... This can do what you're saying... But it can also shake a shock loose without you feeling it... Then the little wheel shake transfers through the loose suspension piece and turns into a scarry thump...

When it happened to me the wheel was out of balance, but not the source of the noise... Check your shafts and balance, and go ahead and check for any missing bolts just in case... A shock shaking a third millimeter into a sheet of metal under the hood sounds like the end of the world...

The only other thing I can think of that you might not is a caliper bolt walked out and the brake is slapping... Would explain a brake vibration, and i've done it Out of balance wheel shook the spindle, but not me... I didn't notice till the caliper threw the bolt... One problem caused by another... Ofcourse this assumes you don't just have a belt seperating in a bad tire... Maybe this helps... Stay safe!

yeah imma check out the brakes n **** this weekend. im ordering drilled and slotted rotors front and rear with hawk pads. I think its just the brakes i rotated my tires and stuff a fe wdays ago in a shop class so i dont think its tire related. Im guessing its the breaks or a bearing in the front somewhere. We have a bearing on each side of the front axle correct? my old truck did in the rear is the reason im asking. Ill check the suspension aswell. its nothing in the trans and motor for sure becasue i throw it into N when it starts making the noise and it still continues so its something that is being caused when in motion of about 30 mph and higher... but for some odd reason it only makes the noise when your going perfectly striaght down the road. a slight turn and it goes away????

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hogan 3inch DP u bend delete ,180*tstat, autolite 104s, LED interior, 4" FWI, 2000watt system, bullitt rims, zzp pistons, pems, alt rewire, thrush muffs, 3.4 zzp mps, transgo shift kit, triple edge performance trans. autometer triple pod :SOON: urlosn HPT PCM tune, HEADERS, 1.9's

today a family friend thats a mechanic is 99 percent sure i have warpped front rotrs is the issue so im getting drilled and sloottted 1's all around in about 2 weeks =]

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hogan 3inch DP u bend delete ,180*tstat, autolite 104s, LED interior, 4" FWI, 2000watt system, bullitt rims, zzp pistons, pems, alt rewire, thrush muffs, 3.4 zzp mps, transgo shift kit, triple edge performance trans. autometer triple pod :SOON: urlosn HPT PCM tune, HEADERS, 1.9's

umm i no this isnt safe but lately it got louder the thump thump thump noise.... so i jacked my fron end up and threw it into d with tires of the ground i still here to noise wtf?? are these halfshafts things bad?? how easy are they to replace? how can you no for sure if thats the problem thanks guys

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hogan 3inch DP u bend delete ,180*tstat, autolite 104s, LED interior, 4" FWI, 2000watt system, bullitt rims, zzp pistons, pems, alt rewire, thrush muffs, 3.4 zzp mps, transgo shift kit, triple edge performance trans. autometer triple pod :SOON: urlosn HPT PCM tune, HEADERS, 1.9's

I had this same problem and it was the halfshaft. It wasn't too bad to replace but we replaced the ball joint(I think, I can't remember for sure right now) and it was a pain to get out. We had to drill out the bolts and it was just a mess doing it. It ended up taking an extra couple hours because of that.

im still thinking its the rotors badly warpped "cuz they are" anyways after i get my d/s rotors n brakes on next weekend ill let you guys no if its still thumpin. any pointers on anything it could possibly be jus tthe rotors right?

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hogan 3inch DP u bend delete ,180*tstat, autolite 104s, LED interior, 4" FWI, 2000watt system, bullitt rims, zzp pistons, pems, alt rewire, thrush muffs, 3.4 zzp mps, transgo shift kit, triple edge performance trans. autometer triple pod :SOON: urlosn HPT PCM tune, HEADERS, 1.9's