Broken Differential mounts
 

Hi,

I have abit of a problem, both of my main differential mounts going through the bushing is broken. They both snapped (the nut) when they got removed, (Please no comments saying you should have used heat and so on, it was done...)

What are my options here? Are they welded on stock? Can I cut it out, drill a whole and put a nut on the back?

Thanks,

I'm having trouble envisioning what you are describing. A photo perhaps?

He snapped the diff bushing studs.

GG. Time for a new subframe.

I'm having a hard time visualizing what you're describing. Are you saying the studs on the sub frame were destroyed? Post up a picture.

That's kind of what I was thinking.

Fortunately, used subframe are cheap. $200-300 on Ebay.

I would imagine that you could probably drop the subframe, drill it out, and weld some new bolts.

You're swapping the subframe.

yup, you have to drop it anyways. welding in some good quality studs should be an easy task for a welder.
with the money saved, maybe sand blast and powder coat it while it's out, too. :)

Here is a picture https://gyazo.com/7884a9447e05a8166b5d73c81836ded6

Yup, that subframe is coming out.

Be careful while unbolting it from the body, lots of PB Blaster and heat, or your next thread will be titled "I accidentally pulled a couple of the studs which the rear subframe attaches to out of the body," along with this photo:

https://cimg5.ibsrv.net/gimg/www.mia...d9ac2ad1d3.png

Once you've done that, the next repair involves cutting the car in half and then welding it back together:

https://www.miataforumz.com/attachme...ine=1312996907

Haha joe!

Ah fock, Then I have no excuse to change all the bushings in the rear then :P

Is the nut on the back a really bad idea ?

A nut on the back is fine if you can get a wrench on it when it's in the car. I've actually never taken the rear subframe off a Miata (one of very parts that have never been removed from my car), but I'd be kind of surprised if there's enough room.

--Ian

The problem here is that high-strength bolts of this length are almost never fully-threaded.

Honestly, there's only one good solution here. Drop the subframe, drill out the old stud, and have a pair of new bolts welded in.

Take the opportunity to have the subframe sandblasted and then powder-coated while it's out. You'll (hopefully) never have another opportunity.

Welding in studs is a terrible idea. You have to drill the old stud out accurately enough to install a new bolt in EXACTLY the same place, twice, because if you mess up either one, it throws all the driveline angles off and the car will vibrate and rattle for all eternity.

Alternatively, while you have the old subframe out, you can throw it in the trash, get another one for $100 or so, and ensure that the studs are in the right place.

You would be a fool to attempt the former option when the latter is available.

Hm, I hadn't considered that. Yeah, I agree.

--Ian

It could be fixed, but given the prevalence of replacement subframes it is easier not to. I would think (and am probably wrong) that bolting in the diff housing would locate them properly. I looked at that part of the subframe once, on the top side there is a round, maybe 2" diameter piece that is welded from the top, that I assume the threaded portion is attached to, but once that is removed there's no telling how many other ways the stud is attached.

https://cimg6.ibsrv.net/gimg/www.mia...0b1b957e34.jpg

Lol @ Joe using my rear cutaway picture. Haven't thought about cutting that car up in years.

thank you all

i am looking for a New subframe to replace. Might as well sand blast, powder coat everything and New bushing while Im at it :)

And don't forget the anti-seize this time ;)