Trans fluid change. What type of fluid?
I have a tf999 in my 89 YJ that I just purchased. I discovered that the trans and tcase came out of a 94 model while I was replacing seals over the weekend so I am sure this is not the factory fluid. I dropped the pan to drain fluid and change the filter this weekend. The fluid was very clean that I removed. I picked up some ATF+4 and started thinking about the fluid that was in the trans. Who knows what type of fluid I drained from it. Dex/Merc, Dex III, or maybe ATF4??? I am not sure what needs to be done at this point. I do not want to add fluid creating a bad mixture that will kill my trans. I don't think these will mix. Has anyone ran into this before?
1989 YJ, 4.2/TF999