I have tranny problems after I changed my tranny oil?

I have an 89 Nissan 240. I changed the tranny fluid on it last month. When I did it, I didnt have the filter kit with me so when the fluid was changed it was just the fluid that got the change. I use RTV and let it dry for about 2 hours then I bolted it up. I test drive and thats when I learn that first gear slips now. Month later sister in law is driving it and occassionly putting in Lucas Oils Tranny Fliud treatment. Says now that it revs at 4-5. I am assuming that thats not in the neighborhood BECAUSE it usually at 2-3.5 rpms in the freeway. And if she meant to tell me that its in residential that I know I wouldnt be here asking this question. Any ideas?I have tranny problems after I changed my tranny oil?
You used the wrong fluid not all fluid is nissan compatible.I have tranny problems after I changed my tranny oil?
I would take it to a tranny person to have it checked out you don't wana mess with things like that. Either way that lucas oil didn't help. It's better safe than sorry.