I am trying to changed the trans fluid in my 2000 TJ. Hopefully before I go wheeling this weekend. I have a NV3550 trans, and a Warn engine/trans skid plate.

First question, what is the Hex Key size for the drain and fill plug? I thought it was 17mm. I thought wrong.

Second question, is there any way to remove the drain plug w/o completely removing the skid plate?

My 2000 TJ uses a 17mm allen bit. Don't know why yours is different.

...think that you will have to remove the skid.

I didn't own anything that would fit that plug.

Ended up welding a couple nuts, of the proper size, to a bolt and made my own tool.

Did mine with my skid off. Never tried it, but I think you'll make a mess if you try it with the skid on.

Well if you want to drain the trans without removing the skid plate take a shop vac, a old fuel line or washer fluid line, some duck tape over the end of the vac to hold the line in place and stick it down the fill plug.