How can i remove a stripped NUT (not the bolt)? Any suggestions?

If you can get to it bolt cutters or use a hacksaw blade cut the bolt!

Vise grips would be my best answer, but since I know those won't fit, (you know too), the next best thing I can think of is to invest in a "Rotary Drill" tool. They sell attachments such as tiny grinding wheels and cutters. If your careful and patient, you can cut the nut off the bolt, or cut the nut on two sides to get a grip with a socket or something. The cutters are pretty fragile, so don't bend them when you use them. Keep at it, but go slow. You'll eventual get that nut off. Sometimes cutting it off, especially in tight spaces like this, is the only way. That's what makes the Rotary Tool so valuable, as you will run into other situations that will require this later on in your life. It's worth the investment of about $70 to buy one. If you're careful, you'll be able to cut that nut right off without even touching or disturbing the threads on the bolt.

File the opposing sides of the nut flat. If you are able to put a little heat on the nut, it would definitely help. Then place the vice grips on the flat surfaces [not too tight] & gently remove the nut.

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There is a common device called a nut buster--sold by JC whitney type places and prpbably auto stores generally. It applies pressure and cracks the nut. Then it will come off easily. You can also split the nut with a chisel and hammer but then you might bent or damage the bolt.

Most hardware stores sell a nut removal set they look like nuts but have backwards threds like an easy out that will cost you between $20 & $30

Had the same problem with a 17mm drain plug, bought a gatorgrip socket, worked like a charm. Last resort- chisel and drill out.

I had about the same thing happen i used gator grip channelockes they were thin enough to fit in and gave enough bite to grab they are considered a water pump plyer got them from auto parts store

there is a tool at sears called bolt out that can also be used on nuts works great

Cut it off with a die grinder if there is enough room but if there is nothing wrong with the transmission leave it along for now.

Vice grips or a small pipe wrench.