If the trans is slipping or showing signs of malfunction you are on borrowed time. You can install a shift kit, use additives, change fluid but you still face the inevitable, a rebuild. I say save your money, do nothing, and put your money towards a rebuild. Drive the trans till you can't stand it anymore then order a TEP trans. Everytime I have tried to keep a dying trans going a little longer by sinking money into it I have regretted it and ended up wasting money that could have been used for a rebuild.
