vibration on decel under car

[BIRDCLAWTSi]

Alright, As stated, When i am coming to a stop and downshifting, There is a wah wah wah kind of noise that is coming from the rear underside of my car. It does it most prominently in 2nd gear, And only from about 4k until i stop. The strange thing is that it stops when i pull up on the parking brake. I put it on the lift and checked everything, The parking brake cable is scure, The is nothing loose underneath that i can see. It almost souds like the spoiler vibrating but it is defiately not. I cant get it to do it on the lift, I replaced both carrier bearings(unrelated).I wish i could get it to happen when i am not driving. It is driving me crazy.

 

[nothingfiction]

sounds like your brake rotars are warped to me.

 

[falcon8r]

If the E brake quiets the chatter the rotor is bad as ^^^ stated. If the rear diff has wear, it will make some noise on a decell at particular rpm..ie frequencies. With lots of backlash, some cars will vibrate loudly. Tres..

 

[Derock2gspyder]

ya i would say wheel bearing or maybe rear end or u joints! check all suspension and fluid in rear end let us know!

 

[BIRDCLAWTSi]

Thanks for the replies, The rotors are good, I just replaced the carrier bearings, I am thinking it might have something to do with the rear subframe mounting bushings or the lash in the rear diff. When i pull the e brake it stops, It only does it at certain rpm's and mainly in second gear. The sound/Vibration resonates, The strange part is the e brake, When i step on the brake pedal it doesnt stop, Only the e brake. I banged on the gas tank and there seems to be a baffle that vibrates in there but i really dont think that is it. I took the fuel pump out and checked it out, There isnt anything really loose in there. This sound is litteraly making me loopy. I have to find it soon or i will go nuts! Has anyone adjusted the lash in the rear diff? I looked on alldata for info, It tells me how to check it but not how to fix it. I looked around and found some info about shims but it was vague.

 

[ThomasG-1b]

So your saying that when you pull up the e-brake when your slowing down it goes away? Or when you have it lifted? And when you are slowing down does the rear end trail out at all? Like if the calibur is stuck open.

 

[black_gst]

did you check all the rear differential bushings make sure all the bolts are there and that the bushings are worn badly?

 

[BIRDCLAWTSi]

So your saying that when you pull up the e-brake when your slowing down it goes away? Or when you have it lifted? And when you are slowing down does the rear end trail out at all? Like if the calibur is stuck open.

When i am slowing down and pull the e brake it stops. I can't get it to do it in the air. The caliper's are not siezed, The pistons go in and out, the slides are well lubed and the hardware is new and lubed. Pads are a month old. It is definately not a brake related issue. Not to mention the wheel bearing on the R/R is brand new, The left side is good, No play or noise.

I should mention that i have only the left side e brake cable connected. When i bought the car last year, Both cables were disconnected, The right side was siezed but the left wasnt. I connected the left side cable and have left it alone ever since. That being said i think it has something to do with the e brake only applying resistance to one side. If it is the rear diff, The resistance on the one wheel might be enough to balance the slack in the diff, Not letting both wheels spin at the same speed. Just a thought. Other than that, The rear diff and sub frame bushings are in shitty shape, They do not appear to have play but with 3000 pounds coming to a stop they might just be making some noise. I checked the slack in the driveshaft and it doesnt seem bad at all. I just changed the rear diff fluid abot a month ago with some royal purple max gear, It made no difference. I really need to have someone drive my car while i hang out the side, I wonder if it would do it on a dyno?.

 

[shockracer]

i bet it would do it on the dyno, i know mine would.