It might be a stupid question but I need help. I have a full size jimmy with a TH-350 tranny that decided to shit out on me today. After a little bit of mild wheelin, I got back on the road and it would go through 1st and 2nd fine but wouldn't hit 3rd. Occasionally it'd go from 2nd to what kinda felt like neutral until I gave it a bit more gas, then it'd jerk back into 2nd momentarily. After a few more miles 2nd stopped working too. Had to crawl home going about 20 mph

I checked the vaccuum line going to the modulator and it seemed to be ok. Any other ideas? Thanks alot.