904 tranny problems

I know its been a while but still can't figure out what's going on I changed the filter filled the tranny and still not accelerating normal. I jacked up the car to check the brakes like fishy said and the front ones were good my rear tires I'm not to sure how to check those does the car have to be in neutral. On top of that I'm leaking tranny fluid from the shifter linkage on the tranny.