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'CLANK" Sounds Like Uni Joints, but...

ronemca

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2016 M/T PP
12K miles
OE drivetrain & suspension
No damage/no bizarre parts/all lug nuts secure (checked)
Exhaust secure (checked) And I've kicked the tips around to see if something contacts - nope.
Spindle nuts secure (checked)
Diff bolts intact (checked)

Sitting still...flat & level pavement...clutch down...select reverse...lift clutch...

CLANK

Sounds like it's coming from beneath the center of the car, but could be further aft.

I can sometimes create the same sound if I select first gear and release the clutch, but it's usually easier to reproduce & more frequent when selecting reverse.

It's just at the first .5 second of engagement before the car begins to move.

If the stick is in reverse, I can make it CLANK - CLANK - CLANK again & again by depressing & releasing the clutch.

It doesn't respond to bumps in the road - only the first few sudden degrees of torsional rotation of the driveshaft when the car is stationary or b-a-r-e-l-y moving.

It sounds exactly like universal joint(s) to me...but with barely 12K miles??

Full disclosure:
The exhaust (new; Magnaflow CBE) and the tranny mount stiffener (new; Whiteline) were both done last Sunday by me. That's how I know they and those other things are secure.
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ronemca

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Did some more experimenting this afternoon (in reverse)

I found that when I release the clutch the sound is more like when you flick a ruler that's hanging off the edge of a table; it's more like a rapid fudda-dudda-dudda sound rather than a single clank. Very odd.
 
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ronemca

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As you can tell, this is really bugging me. The paranoid part of me is saying:

"Oh no! Uni joints! CV joints! Sheared diff bolts! Egad!"

But the logical part of me is saying:

"It has to be related to the changes I just made."

Which makes the cause 20% exhaust-related and 80% tranny mount insert -related.

Sadly we are in the middle of a fierce ice-storm here in Southern Ontario...so there's no way I can get a look underneath. But in the meantime...

Can someone please provide the torque spec for the four 18mm bolts that support the rear tranny cradle? I tightened them with a box end wrench to 0.8 gorillas...but maybe that's not enough(?) Or perhaps one of them has loosened slightly(?)

Thanks, gents!
 
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rlyons13

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Yeah, I stiffened the trans mount and put in a one piece driveshaft. Started hearing the clank like you. Popped under the car, expecting the U-joint on the driveshaft, but they are solid and the play is in the transmission. Guess the softer bushings and two-piece driveshaft absorb the play.
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