So my th400 I got a new winters shifter and can't get the nut off the trans to get the old arm off and don't want to break the shifter shaft. What are my options
I Wish I could get an impact to it. Without dropping's it down there is no way. How much force can be used without damaging the shaft. And is it a regular thread or reverse
I agree. It's rare to see a shift shaft nut that is seized or rusted. Mainly because there is pretty much always fluid seeping or leaking around that seal.
So a flare nut wrench, aka brake line wrench, works excellent without stripping the nut. Don't be scared. Put some booty on it. It has stops inside that are plenty strong. I bet you get it loose without harming things