So I know everyone typically uses mercron 5, but I may have an alternative that I am going to try when I fix my trans pan leaking and complete a jmod. I am going to use Allison Transynd. Its Allison brand auto transmission fluid that castrol makes. It costs 36$ a gallon but I get gallons of it regularly working at a Freightliner Dealer that is also a huge Allison firm. I have been pumping the stuff into My C6 in the idi, and also my 44re in my V8 Jeep, with no negative results to report, so I guess the next victim would be my Tbird. I think it may also offer longer service intervals. Allison quotes 50k, but it may be also because typical units have 19-42 quart changes, and twin filters. So I am not sure. I guess I can change it, then have samples sent out every 10k through the Allison service and see how the trans fluid does.
1995 Ford Thunderbird 4.6 LX - SC wheels, enlarged rear sway bar, full sound system, cut mufflers, PST 1 1/8" rear bar, Eibachs, Mark 8 LCA's, Al housed 3.55 gearset, cut mufflers
2011 BMX X5 Xdrive50i - BMS Stage 1, Cut Muffler
2005 Jeep Grand Cherokee 5.7L-Her stock DD
1984 Ford F250 6.9 IDIT - head studs in progress