Rear end shudder?

[Mileage]

(Video on post #6)

Hey guys,

Because I've gutted my car, I can hear all kinds of things in the interior. Two sounds in particular are driving me up the wall (besides the diff whine lol)

At parking lot speeds, especially in first gear, if I let off the throttle, I can hear slight knocking from the back as the car jerks back and forth twice or three times. It also happens in every gear if I abruptly get off throttle/abruptly re-engage the clutch after changing gears. It's not a violent knocking, it just sounds like something is loose.

I don't think it's the diff bolt, the bushing and bolt look fine. I have a hard time believing it's my subframe bushings (AKG Poly) or a failing subframe mount (AKG subframe weld-in). RTAB are poly and diff mounts are poly. Maybe rear shock mounts? Guibo?

The next sound is a rear end clunk. It happens if I abruptly depress the clutch or shift gears faster than usual. I've been told this is normal to some extent. If I shift gears slowly enough, the clunk isn't an issue. I'm thinking guibo or center support bearing. Any other areas I should peek around this weekend when I slide under?

Any input would be greatly appreciated! Enjoy your weekends!

[Ex36]

I was going to guess the center support bearing allowing too much drive shaft play, but that's just a WAG.

[TostitoBandito]

The fact that the car moves laterally seems to point more to something in the suspension or maybe the diff doing some weird asymmetric locking. The driveshaft support might make it clunk, but it doesn't seem like it could make your rear end bounce around like that. Rear shock mounts are a good idea to check.

Also might look at the rear springs/perches. Depending on your suspension, you could have a spring popping off a perch on one side when the suspension is unloaded, or something along those lines.

[Mileage]

I was going to guess the center support bearing allowing too much drive shaft play, but that's just a WAG.

Your guess is good as mine. CSB is a pain to replace, but I may have no choice.

The fact that the car moves laterally seems to point more to something in the suspension or maybe the diff doing some weird asymmetric locking. The driveshaft support might make it clunk, but it doesn't seem like it could make your rear end bounce around like that. Rear shock mounts are a good idea to check.

Also might look at the rear springs/perches. Depending on your suspension, you could have a spring popping off a perch on one side when the suspension is unloaded, or something along those lines.

I'm thinking suspension too. The springs are directly on the perch with no rubber so maybe they are moving around? RSM is gonna be next to check. Any idea on how to test them for wobbliness?

[hli]

Mine does the same thing. I've replaced the CSB, guibo, motor mounts, and have visually inspected everything else in the driveline. I originally thought my DMF had failed but eventually my conclusion was that it was due to gear lash inside the transmission/rotational inertia of the clutch. Try this: get the car rolling in 2nd at around 1.5k RPM, then clutch in and shift quickly into 1st (without letting the clutch out). If that creates the same clunking noise, you can rule out the DMF. Then it's just a matter of getting under your car with the car in gear and handbrake off, and manually moving your rear wheels to see where the play is.

[Mileage]

Didn't want to create a new thread so I'm bumping this one. Finally had a chance to get under my car the other day and film the sound. The car is on jackstands (no load) and I was simply engaging/releasing the clutch in first. Since the diff/subframe have no movement, could it be the driveshaft U joint? I also noticed that the car has a weird whining noise, but only when decelerating. There is also a constant whine at speeds above 40 mph. Wonder if the pinion bearing went bad as well. Any thoughts?

[TostitoBandito]

How do the diff and transmission fluid levels look, and is there any debris in there?

[Mileage]

How do the diff and transmission fluid levels look, and is there any debris in there?

Hey thanks for the response. Diff fluid was changed last month, haven't checked the transmission fluid. Would that cause that clunking sound? It also clunks upon engaging first gear/jerky application of throttle

[TostitoBandito]

It might not tell you much, but probably wouldn't hurt to drain and refill the trans. You can check the old oil for any signs of metal debris. In any case, it's not very expensive and might need to be done on the car anyways.

Just watched the video you posted above. It looks like the diff flange is rotating unevenly. Watch the gap between the start of the flange and the diff as you have it in gear and it's spinning. Seems like the noises are also coming from there, so I'd speculate that there's something amiss inside your diff (or maybe just the flange).

[TH3 Shifty]

RTABS make the car move side to side when bad.. check them out

[Mileage]

It might not tell you much, but probably wouldn't hurt to drain and refill the trans. You can check the old oil for any signs of metal debris. In any case, it's not very expensive and might need to be done on the car anyways.

Just watched the video you posted above. It looks like the diff flange is rotating unevenly. Watch the gap between the start of the flange and the diff as you have it in gear and it's spinning. Seems like the noises are also coming from there, so I'd speculate that there's something amiss inside your diff (or maybe just the flange).

Yes I noticed the flange movement as well. Makes me think it is the Ujoint on that end or pinion bearing (which would explain the whining) If its a combination of both, well, that would suck.

RTABS make the car move side to side when bad.. check them out

Car has Poly RTABs so I highly doubt that they would cause a metallic sound. Also, the rear is jacked up and unloaded in the clip I uploaded, so I don't think it's suspension related. But thanks for the response

[Mileage]

Update on this:

Happened to be my rear diff. Disconnected the drive shaft from input flange. When rotating input flange, there is ~5 degrees of play before the wheels start moving. And when rotating beyond the play, it makes that clank noise in the video. Guess it's too much back lash? Oh well, already bought a new driveshaft and gonna look for used diffs. ///M problems can be expensive

[TostitoBandito]

If you wanna go big, diffsonline.com is fantastic. I got my 3.46 from there.

[Mileage]

If you wanna go big, diffsonline.com is fantastic. I got my 3.46 from there.

Nice, looking for a 3.38 myself. Diffsonline offers quality stuff, but maybe a little out of budget. The PO used to powerslide this car on semi slicks so not surprised the diff is toast lol