Driveline noise - help please

My car started making a strange noise. I noticed this a few weeks ago when pulling into a parking lot, stopping, and putting into reverse and backing into the spot. It'll emit a small thunk, what feels like slop somewhere, and has a medium/high pitch metallic sound to it. It sounds and feels like its coming from the center/rear of the car.

Over the last week or so, it's been getting worse. It'll start doing it both directions from a stop (not every time) but can replicate pretty consistently.

I haven't looked at the car, or taken to the dealer. I am planning on inspecting it on a 4 post lift this weekend, and putting a wrench on everything with a few friends.

PS, car is a 2015 GT PP manual.

Any thoughts?

UPDATED WITH VIDEO:

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I have had this same issue after installing IRS solid bushings. Took it to a shop today to see if they can figure it out. On the phone today, they said it simply needed some adjustment. We will see.

Mine turned out to be the rear axle nuts being a touch loose. Tightened them up and hasn't made the noise since, 2 days so far...

Competition Orange said:

Mine turned out to be the rear axle nuts being a tough loose. Tightened them up and hasn't made the noise since, 2 days so far...

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Thanks for the update. I'll definitely keep that in mind if it comes back from the shop still popping.

That is a strange noise. Suspension or bushing mods?

steveespo said:

That is a strange noise. Suspension or bushing mods?

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All the above. I came across some information that the axle nuts are one time use. So when I removed the half shafts or axles and re installed the nuts, they weren't up to spec. Took it to a shop, they fixed the problem. Hopefully they bought new ones. Will find out tomorrow.

BMR handling springs, eibach sways, no bushings.

Axle huts seem to have been it. Haven't heard the noise since I tightened them down a few days ago.

The REAR Axle Nut Torque is 98ft/lbs plus 45 degrees.

Ford Also Recently Changed Part Numbers for the Nut from CV6Z-3B477-A to CCPZ-3B477-F. The new nut is now single piece not the separate washer and nut.

Optimum Performance said:

The REAR Axle Nut Torque is 98ft/lbs plus 45 degrees.

Ford Also Recently Changed Part Numbers for the Nut from CV6Z-3B477-A to CCPZ-3B477-F. The new nut is now single piece not the separate washer and nut.

Click to expand...

Yeah, mine is expertly tq'd to that spec ;)

If it comes loose again, I'll grab the updated part number and use the "correct" tq spec.

So what is making the noise with the nut loose? Axle splines moving back and forth? Or CV joint movement? I am assuming they weren't backed off a full turn or more.
Steve

NO clue. I was shocked it went away since I only got such a small amount of movement out of the nut.

The spline is pretty tight (not any slop) the axles push out to the bearing back. Unlike the front nothing can fall off. It's a pre-loaded bearing so the torque does (should) not effect the bearing. The nut simply locks the axle in.

My only concern would be if you develop any Adv. Track or ABS issues. There is a 3 pronged washer between the axle and hub.Those have broken in the past.

Old nut on top, new nut on bottom in pic.