stuck in 1st gear

i have had this 79 el comino for the past month and its been giving me plenty of greef.
it has a 350 ci engine and i believe a turbo 350 transmission-i dont know exactly what kind...

i just changed the speedometer gear, the gear in the end of the transmission that rotates the speedometer cable, and i've heard that pieces of that gear can jam up other parts of the transmission.
the problem is that now the truck wont shift in gears other than park, reverse, and 1st on drive. it wont shift into 2nd at all when it did normally. i noticed that when i was driving it before it hesitated before shifting into gears, giving a second or two in neutral before shifting, but i never drove it more than once or twice a week. over all since i got the truck ive put on less than 3000 miles.

so basicly i was trying to figure out what the problem is and how to fix it. ive been suspecting a vacume leak, however; it might be a piece of plastic from the speedometer gear, if you know what could be my problem and how to fix it, i would be greatful

thanks
krazy karl

 

unplug the vacum line coming from vacum modulater on transmission start engine should have vacum there if it doesnt trace it back to engine and repair leak, should also not have any transmission fluid in vacum line indicating a bad diaphram in the vacum modulator which will need replaced, typically they will shift but it will be very late, if the above checks ok probably has internal failure and should go to transmission shop.