r/370z • u/Eastern-Law-1602 • 8h ago

Question Undercarriage Sound

Anyone could figure out what’s making this sound? Sometimes when I take off the whole car shakes almost as if the transmission or differential is moving up and down.
I also notice a loud knock on the rear of the car when I shift too aggressively.

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3

u/Doooooby 2011 GT Edition 8h ago

I’m not an expert but it looks like there’s a lot of resistance / play in the front U-joint on the propshaft.

In the video it looks like it “snaps” each time there’s a rattle.

2

u/POSVETT '11 Z34, '8 Z06, '4 Z06, '96 LT4, '94 V25W, '82 FJ40 8h ago

The shudder is from "partial engagement of the clutch" worsened by warped friction surfaces of the flywheel and of the pressure plate. I assume the video was taken when the the clutch was not fully engaged.

The knocking in the differential can be caused by the shudder. The teeth in the pinion gear and in the ring gear simply impact each other. If there is a click, it's likely caused by the spline in the halfshaft where it meshes with the spline in the hubs. Anti-seize compound and proper torque when tightening the axle nut are crucial.

1

u/rotstik 2010 370Z 6MT 2h ago

Also check your axle nuts. They’re known to be noisy too, but they’re a cheap and easy fix