C6 trans will not up shift into 3rd

[Blueoval]

My 1970 F100 with C6 will not up shift into 3rd. I-2 ok if gear selector in 2nd. If left in D will struggle from 1-2, once in 2nd will not up shift. I replaced modulator, trans fluid and filter. Any help would be appreciated.
Thanks.

[motzingg]

I've looked at several econoline vans on craigslist with this exact same problem. I'm very interested to hear if someone has a solution.



My automatic transmission knowledge is more or less limited to fixing/adjusting the shift linkage. I always start there. I've fixed several volvos, a peugeot, a mazda, a subaru and a cadillac that were destined for the scrap yard just because of a loose and dodgy shifter.

The Volvo 960, the guy actually said he would give me if i could figure out how to get it out of his driveway. It took me less than an hour and when i was done I felt so bad for him that I told him to keep the car and accepted a case of beer as payment.