I have a 74' f250 ranger xlt trailer special with a 460 and c6 tranny. Its very difficult to shift from any gear to any other gear it but it goes into gear and stays in gear. Also when you put it in gear it lurches forward. And when your in gear stoped and u get on it you can feel it slip for a split second. I bought this truck as a project its my first car. It starts great and is strong.

 

Except for the slipping on startup it sounds like either the vacuum modulator is bad or the vacuum line going to it is blocked, disconnected or cracked.
Pull the line of the modulator and see if fluid leaks out, if yes, the modulator is bad. If no fluid leaks out, it still may be bad. Check the line from one end to the other to see if that could be the problem.

 

Also make sure the fluid level is correct

 

are you saying it is difficult to move the gear selector between PRND21? If so, the shift collar cracks internally and can cause these symptoms....

 

Yes it is hard to move to gear selector and when it goes in it lurches foward or reverse obviously depanding on which gear you put it in.

 

Yes fluids are good

 

OK, then check the modulator like Mike suggested, if that looks ok I would drop the pan and see if it's full of gunk or any metal pieces.
The C6 is a pretty tough tranny but they do wear out.
Lets us know what you find and good luck to you.

 

Ok i definatly will thanks for the help