transmission leak

why is my 99 couger leaking transmission fluid? i changed the speed sensor and now i have a leak. seems like its getting back pressure.

Need more details. Where is it leaking from?

seems like its pushing back through the bottom of filler tube.could it be coming from a breather or somewhere else.doesnt leak all the time.but alot.when it leaks unable to put fluid in pressure wont let fluid go down filler tube.

Head over to the NECO forums(newcougar.org) and search. I seem to remember someone else having this same problem. I don't remember what the outcome was though. Good luck.