I feel like I'm asking so many questions that have already been asked, but i need it explained in "learning" terms... My 75 Comet won't shift on its own. Fluid, filter, gasket, etc are fine. I now know (thanks to the good people of this board) that it must be my modulator/vacuum modulator hose... Well, i lifted my car, found my modulator, but which one is my v.m. hose???
There is a tube (metal) that runs down the tunnel from the firewall to the modulator. If the tube isn't there you need to replace it because a hose that long will collapse and give you fits.
One more note on those metal lines... Check them carefully for rust holes! I looked for an intermittant trans problem in my '77 F-100 for months and found mine was rusting when I gave up and started to pull the trans to rebuild it. -Scott H.
how long have you owned the car?did it shift fine before and now you have to manually shift it?there are alot of shift kits that are full manual.if it shifted fine before i would deff.say you are haveing a problem with the vaccume modulator.some times the hose rots or people replace them and put them on the wrong vaccume port.
Found it! And it was pathetic... Gaping holes in the rustiest piece of medal I've ever seen! Putting on a new hose today, thanks a lot guys
Once you get it replaced, you might have to adjust your carb. With the holes in the line pulling constant air into the carb, once it's a sealed system again it might start running rich because the fresh air is no longer there. I'm glad you found it and it was an easy fix! -Scott H.
Don't replace the metal line with a hose! The hose will collapse under vacuum and you will have shifting problems. Get a piece of brake line and fit it to the same place.
