To preface this a few months ago I replaced the rear subframe on my sedan because I suspected that the original one was damaged. The shop that had done the repairs had ordered a subframe but did not install it. After I got the car back the two rear tires were wearing unevenly. The car did not suffer any frame damage so I thought maybe a control arm mounting point was messed up and over looked. After I removed the rear subframe I learned that the repair shop put the wrong camber arm on one side(a straight one as opposed to slightly curved) and did not replace the lower spring seat on that spring bucket.

I swapped over the Z1 diff bushings and subframe collars to the new subframe and put some rubber shims where the lower spring seats would go then took it for an alignment, and everything checked out. But now the rear two subframe bolts keep backing off. I’ve had to re-torque the nuts 3 times now, all times I’ve been able to get about 3/4-1&1/4 turns until 88 ftlbs. I put threadlocker medium strength on the most recent time but the creaking that indicates the nuts need re-torquing has developed again.

 

Can you take a photo like this of your car? This photo is passenger side I just stuck my phone in. Curious if you are missing anyone of the OEM bracing.

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The braces are there. I wonder if the rear brace acts like a washer and needs to be replaced.

 

Thanks for the photos, I would first try replacing both the rear nuts(make sure it's the correct grade) and running a die over the threads to ensure they are clean and good working order. Ideally would also replace the stud but try a die see how that works.

Washers don't need to be replaced unless they are deformed. I'm sure the rear brace is fine, just wanted to make sure it was there.
​​​​I'm assuming you using a torque wrench for these bolts?

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Yes, I used a torque wrench. I will try getting new nuts and take a look at the braces to see if they are deformed. Thank you

 

You can also try loosening all the subframe bolts shaking the subframe to make sure it's not bound on anything then re-torque in a cross pattern 20ft/lb, then 88ft lbs.

 

I ended up re-threading the studs and nuts and that seems to have solved the issue. I will keep an eye on it but so far after about 150 miles the torque has held.

I searched for a while trying to find the thread size for the studs and couldn’t find it so putting it out there. M14x1.5

 

That's awesome to hear! Glad it helped.

 

Why not some blue/red locktite?

 

I put some orange thread locker on a few weeks ago but it didn’t hold. Threads were dirty. I didn’t put any on after re-threading everything but it seems to be holding now.

 

I'm unfamiliar with orange, just red and blue. The former requiring heat to undo, the latter not. I suppose clean threads are important for adhesion.

 

Orange thread locker is supposed to be somewhere between blue and red when it comes to strength and doesn’t require heat to remove

 

No kidding...

https://www.permatex.com/products/th...range-gel-5-g/

Never heard of such a thing, but apparently it does exist.