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Grinding/Rubbing noise coming from rear on acceleration
So this noise started out as a very faint "rubbing" noise that sounded like tire rubbing and thats what i thought it couldve been because i have pretty tight fitment, however about 2 weeks ago the sound got really bad on an hour drive back home in traffic. Basically went from sounding like a faint rubber and fender contact noise to now sounding like metal on metal friction. it doesnt make the noise until the car is warmed up and only makes the noise while accelerating. Once my foot comes off the pedal the noise goes away. I thought it was my axle or wheel bearing so i replaced both with no luck, also did a diff fluid change and there was no metal in the fluid. Im considering buying a diff but i want to hear other opinions before throwing unnecessary money into the car. Also i have jacked the rear end up and went through the gears to try and replicate the noise and it wouldnt do it, only makes the noise when the car is on the ground. Videos with the noise are linked
Sounds like aftermarket exhaust installed. Check your clearances around the rear subframe and sway bar. Make sure the exhaust isn't rubbing anything, this is more common than you would think.
Once verifying the exhaust is all good, I would inspect the driveshaft U-joints for excessive wear/play.
One other common rear end noise source are the upper strut bushings, but I doubt that is the issue in this case.
Good Luck!
-Icer
does it only make the noise when you accelerate somewhat hard or anytime you lightly touch the gas pedal? If it's not noticeable even on a light touch, then you can rule out things like drive shaft, u-joints, axles. If it's on heavier acceleration, then I would check the rear differential mounting bolts and bushings. The bushings could be worn out which would cause the differential to dip forward on acceleration.(both the horizontal and vertical mounting points).
it will make noise on a slight touch of the gas pedal only if im going uphill otherwise its really only on hard acceleration. Just purchased a vlsd i plan on swapping in tomorrow, if that does not fix the problem well at least i wont have an open diff.
If you're replacing the diff, now is the time to replace the OEM diff bushings. Go with some Polyurethane (I'm using Whiteline) or even hardcore mode with solid bushings, your call. The bushing removal process is not fun. There are multiple vids and threads out there on different methods to achieve this. But the proper tools would be something like the Z1 bushing removal tool for the rear subframe bushing (primary piece that fails) and a shop press to remove the horizontal bushings from the diff case. Otherwise there are writeups on how to make your own tool or use other tools to cut/hack/remove the old bushings. Once it's all said and done, it's worth it!
I hope the diff solves your issue. But after your last bit of information about being on the gas while also going up a hill or a hard pull, has me thinking this could be related to your clutch or transmission.
Good Luck!
-Icer
yeah, If the bushings are shot then the diff will twerk when you give it torque and that would explain the noise you're hearing. these bushings are not easy to do. I bought a shop press from harbor freight just for this job. I think it was $150, 12T. kind of wish I'd bought the bigger one.
The diff is a PITA. I learned what I think is the best way to remove / install:
leave the axles on while removing the bushing bolts. that keeps it from falling. And even if you have a jack it's probably going to fall because but c o g is in a weird place.
last time I installed mine I lifted it up with the jack, installed the axle bolts first to hold it up. then it's a cinch to mount it.
If you have a transmission jack, it's a piece of cake to remove/install, of course this assumes you remove the rear sway bar and exhaust.
Cheers!
-Icer
Edit: Of course not everyone has a trans-jack (I probably sounded snobby when I posted this comment). I purchased the Harbor Freight 800lb unit since I knew I would need to do both a clutch job (drop the trans) and replace my diff around the same time. So for me, it was worth the investment. It can be done with other means, such as your photo above with the floor jack. But using a floor jack is best done with a buddy to help stabilize the pumpkin. These suckers are heavy and will ruin your day if it falls. What I want to know is, how did you support the diff case when pressing out the horizontal bushings with the HB 12T shop press (which I also own)?
thought i would drop in and say that the diff did not fix the noise and my slave cylinder went out again (changed it a year ago) dropping the trans this week to replace the slave/clutch/flywheel and do a trans flush hopefully after all of this money itll be ok lmfao
What year is your Z? Do you have a CSC (Concentric Slave Cylinder, on 07-08 HR equipped Zs)? I really suspect you may have a clutch issue after your findings with the differential. Did you replace the diff bushings during the swap or no? If you have a CSC, get an upgraded unit. Those OEM CSCs are the only serious weak point with the HRs drivetrain (aside from the oil gallery gasket failure).
While you're in there doing the trans work, inspect the trans mount and motor mounts. Also check your transmission's input shaft for bearing play and check your driveshaft U-joints. Replace trans fluid with Redline MT-85 (Good stuff).
Should have a nice running Z once you get it sorted.
-Icer
10-10-2023, 09:54 AM
Grinding/Rubbing noise coming from rear on acceleration
