I recently installed a Tick master, and replaced the slave cylinder in my '99 Z. Drained all the fluid out of the trans before pulling, did the parts swap, and put everything back in.

As far as I know, the trans is stock. I like the new Tick Master, and reverse and 6th gear are much easier to get into. BUT, 2nd and 4th gears feel like they're about to pop out of gear. I'm thinking it's the fluid I used, I can't seem to find Mobil 1 ATF Dex3 fluid anywhere locally. The Chevy dealer was NO help at all, other than telling me that they use dexron 6 now, which is listed as a synthetic. (the guy at the counter didn't know who Tremec was, if that tells you what I was dealing with). From what I'm reading here on the forums, I don't want to put synthetic in the trans. Would Castrol "multi-vehicle" ATF fluid be ok? I believe I put the Dex/Merc ATF fluid in. I threw the bottles out before I could check. I don't want to mess up the trans in any way.