From your description as well as miles on vehicle I would say it is a transmission. What has happened is the clutch paks are worn or the seals are bad. I would bet that the transmission fluid is either dark brown or black which is not a good sign at all. I have never seen the additives rarely work to fix things and normally it is too late for that anyhow.
Thursday, April 20th, 2017 AT 10:44 AM