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Loud rattle on deceleration

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EvanJ

Probationary Member
14
0
Feb 26, 2014
Winnipeg, MB_Canada
Sup fellas! alright so i got an issue, or maybe not, i dont know yet. I have an 98 eclipse gsx and over the weekend i replaced my rear diff bushings to poly ones and did my rear wheel bearings. What im finding now is that when i decelerate in gear i hear a loud rattle coming from under the car. its also notable that if I push the clutch in the noise stops. now is this sound just from the diff vibrating through the hard diff bushings? or is it possible its tranny or clutch/flywheel related? what do ya guys think?
 
Hey sorry for not responding in forever! no the car doesnt make any noise when stopped. I figure its the drive shaft as the U-Joints are starting to go and the last owner to work on the car didnt align shafts on the U-Joints when he installed it. Il update if what happnes with the new U-Joints.
 
Is it a lighter tin sounding rattle, or does it sound like something heavier? I had the heat shield on the stock exhaust rattle really loud at certain rpm. Best to just get under the car and check everything.
 
Check for areas where the exhaust could contact metal. Check the mounts as well. It has been suggested by others that this can be caused from heavier clutch setups with lightened flywheels. There is however an increase in vibration by adding stiffer bushings. The poly bushings do not absorb nearly as much vibration as the OE ones do. The poly transfer more vibration as they are stiffer. This would be further amplified by solid bushings as well. Did you also replace the sub-frame bushings while you were doing all that work?
 
Hard call to make, you need to do some more troubleshooting I would say. Where do you feel vibrations at? If there is a noise /rattle there's going to be vibrations.
 
For what its worth i have the same noise on deceleration with my setup, i just figured it was either my 3" exhaust or my poly mounts/clutch and flywheel setup. Either way its not really something that concerns me.
 
Mine started to do that and it drove me nuts. I spent quite a bit of time under the car looking for loose heat shields or exhaust and whatnot before i ended finding out that it was my rear license plate. I put 3m foam tape on the back of the plate, now all i hear is a wheel bearing moaning. Nuts :(
 
Do you use sprung or unsprung clutch disk? Do you have engine balance shafts removed? Unsprung clutch disks, removed balanced shafts, light flywheel, light crankshaft pulley, stiffer drivetrain bushings will all contribute to drivetrain vibrations caused by engine harmonics. Most heard and felt under de-acceleration.
 
I have the same thing. After getting under the rear end and hitting shit with my hand, I noticed the right rear brake line not all the way tight. Rattling on my strut.

Point is to get under and rattle shit. You'll hear where it comes from. Maybe that helps.

I'm glad I don't hear it anymore. Haha.
 
Hey guys, as thing progressed I forgot about the thread. sorry about that. anyway, the u-joints are all replaced which actually did stop one of the main rattles coming for from the front section of the drive shaft. but there still is the rattle in the back near the diff upon deceleration. I do have a stage 2 clutch with a fidanza light weight flywheel. so ive come to the conclusion that its just general drive train chatter emanating through the solid poly/alu diff mounts. what I was thing thinking was that the subframe is hollow which would amplify noise greatly. what if it was filled with a dense expanding foam? think that would help quiet the noise?
 
I'm trying to figure out the same issue. Nasty rattle from under the car when I let off the gas completely while still in gear.

Everything I've read has been people basically saying that it's just something you have to live with when driving an AWD DSM or evo. Especially with upgraded clutch/flywheel combinations.

It would be nice if someone knew what this was and how to fix it.
 
It's definitively drivetrain chatter, My GSX did this too, and so I replaced the fluid in the transfer-case and which reduced the chatter and then I switched/replaced the gear oil in the Rear Diff, the chatter went away completely. I think I put redline shockproof in there..
 
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