Do i dare tighten this?
 

Now that I've changed my leaking coolant expansion tank and cap, the system must be back to being pressurized, and I noticed this leak from the transmission coolant line:


Attachment 60647


Can I add some teflon tape or the like, or should I just tighten it.

Don't want to break the plastic radiator.

Most likely if you try to do anything to this it will break.
i would get a new radiator. Its probably due.

Until then there's no harm in trying teflon tape. I'm using it more often on my cars.

I dare you.

As I remember (been a couple years) on my '91 the big nut screws directly onto a protuding nipple of the trans coolant tank (not directly to the plastic radiator) with a rubber washer in between to seal the radiator. So..... you should be able to remove the small hose nut, holding a backup on the big nut, then remove the big nut from the trans tank nipple without putting undue stress on the radiator plastic. Replace or seal the gasket and gently tighten it all back up.
But remember, as you loosen the big nut, you are applying force on the copper trans cooling tank inside the radiator, and you don't want to fracture it; that would mix water and ATF, not a good thing. So, if it doesn't unscrew relatively easy, don't get too forceful.

Good luck,

DG

turns out the big bolt was loose - i gave it about 1/2 a turn and its not leaking (knock wood) Whew - that coulda been pricey