Welcome, I'm Chris (aka Moose) I'm an independent contractor here at Just Answer.
Do you know which model transmission you have?
Do 1st and 2nd work in the manual gears but not in drive?
Does it start off in 3rd gear?
The only way I can see this leak related to the the transmission concern is if the oil got into the connectors for the solenoids and TR sensor at the transmission or PCM. Have you checked and or cleaned those connections?
Thanks for asking your question and letting me try to help you.
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