That's the thing, you don't get to it from inside the frame, everything I mentioned is outside of the frame from the bottom side (where the subframe mounts to the frame).

 

So you're saying the stud itself where it meet the frame weld there? Why would going into the frame be a bad idea ?

I am sorry if I can't understand what you were saying >,<

 

Basically... I'm giving you an option to not go inside the boxed frame by cutting it and then having to patch it back up just to gain access to the nut. Ultimately its up to you, I gave you my perspective.

 

HUGE update, the problem has been fixed. I found out what type of design Mitsubishi uses to bolt to the stud. The stud itself is free moving, it has a [square head] and it is in a slightly larger but not too large square boxing. This allows the stud to move a little but when turning the nut onto the bolt it lock because it goes on all four corners. What I figured happened was the previous owner did the clutch, may have dropped the front sub--frame and when reinstalling it used a impact and drove the sub frame up with that nut.

This would eventually allow the [square part of the studs head to give way and become (rounded). This diagram I made, sorry I am not an artist will help a little.




AS you can see from the points I labeled, points A,B,C, and D of the studs head is what was rounded, so by welding some material in that square housing the stud was able to catch on that, and we're all back to perfect

To fix it we cut a small access point into the frame, we ere able to get to the area, and weld around, but not the stud, just a little filler to have that stud grab and work as it should.

Though I would just follow up, if anyone ever wondered if this can be fixed with ease it can be, if you take your time and it right the first time.

 

Can you post some pictures of where you cut please.

I just had this same problem happen or just noticed it.