Can anyone tell me what the best transmission fluid is to use? I've been told that Dextron III/Mercon was a replacement for the Ford Automatic Transmission Fluid they used, but other sources have told me that older cars should use F-Type transmission fluid. I've also been told that if the transmission is original, it should probably use F-Type, but if it's been through a modern rebuild you can use Dextron. I just acquired this transmission after my original was facing a very expensive rebuild. As far as I know, only the gaskets and seals were replaced while this latest transmission was inspected/"rebuilt". I have no idea how old the clutches or anything are. The tag is also missing on this transmission so all there is is casting numbers to identify it. This new tranny looks slightly different than my old one as well. For example, it's tailstock had no inspection opening (so we are using my old tailstock). Both have the vacuum modulators on them, but the new tranny doesn't have the aluminum vent line and the fluid line fittings are different sizes.
Basically I am wondering about what the safest fluid to use is, and for some insight/details into these two transmissions. I'll try to post pictures of the noticeable differences and casting numbers. The silver transmission is the new one. The blue is the old. I've only found one picture online of a transmission that looks like my old one and they said it was a Merc-o-matic.
At this point I'm pretty confused.
Thanks for bearing with my lengthy story lol
Thanks in advance!