Ok not sure if this is the place to ask but here it goes.

While replacing the transmission when I removed the rear support the nut plate broke off inside the frame.

Does anyone have any ideas how to replace or fix the nut plate???

 

You prepared to do some cutting and welding? If not, might want to get a shop to deal with it.

 

Try drilling it out and using an extractor to remove it.

 

Had the same thing happen to me. What I ended up doing(and AFAIK is the only way to fix it) is pull up the carpet and find where the frame rails are from inside the car. Cut a small access hole in the floor and weld new nuts in place. Actually, I welded bolts to some large fender washers, then welded the washers to the inside of the frame rail so the threads of the bolts stuck out down below. Then welded the floor back up. Now I have 4 bolts sticking down that I lift the crossmember up to and put nuts on to hold it in place. Its much easier for me to do it this way than to try and hold up the weight of the trans and crossmember while trying to find a hole with the bolt.

 

Ok here is what I am going to do for others to learn. Since the options are cutting into the frame or floorboard I opted for this. Where the current holes are in the frame I decided to adhere a new piece of steel and weld new nuts on the back. Inserting the new nuts through the old holes. Then weld the bracket onto the frame. Done.

 

That's about what I figured to be the simplest method. Keep in mind your crossmember will sit the thickness of the bracket lower, though this is likely a negligible amount and less than the drop from worn rubber bushings.