what i would do is get the lucas slip and add to the fluid as a top off but to really be safe i would get a suitable clean transmission fluid bucket try to catch as much as your fluid as possible get you a funnel put your new filter in and install your tranny pan and put the old fluid back in your tranny and if you need to top it off then i would add the lucas slip oil even if the tranny fluid is a little low you still can add the lucas slip oil as a top off you can do that to as well