Well, this may be a silly question. But I just gotta ask.

Has any one tried filling the rear differential mount with polyeurothane to make it stiffer/last longer?

I've done this with other vehicle's motor and transmission mounts with fairly good results. Just wondering if anyone here has tried it.

 

seen people drill through the parts and bolt them together, cheap solid mount

 

Stiffer? Longer lasting? Try that little blue pill....

Or maybe this will work.

 

Now, that I might be able to pull off. What thickness would be recommended for the material? 1/4", 1/2", 1/8"?

 

I didn't mic it. It was just some scrap from another job. An educated guess would be .16 gauge. 1/8" should be fine.

 

I see that you're in NC as well. Where at?

 

I'd go at least 1/4 inch.... thicker isn't any more difficult to fab, and it's going to be stronger. You will need that especially if you will be doing any auto-x or racing. Look at the stock mount... it's not flimzy... so don't make a custom one weak.
You should also be aware that sold diff mounts make hella-noise.... you hear road and mechanical noise a lot more.

 

Couldn't resist pimping a pic of my home made diff mount. Not bad for about $8 and some time with a tape measure and drill press. 1/2" angle Iron is MORE than enough for ANYTHING I can imagine ever throwing at the car.

Pic is of a test fit which is why there's missing nuts and nothings tightened down.