Well, the title pretty much says it.  My vacuum reservoir is practically full of transmission fluid.  Is it time for a transmission rebuild, or is there some easy to replace valve that’s failed?
 The truck is a '84 F150 302 automatic 2WD
Your vacuum modulator has failed. Luckily for you it’s not very expensive. This was a common problem back in the 70’s and 80’s.
Make sure you get the right modulator. Very cheap repair.
transman
Thanks ya’ll.