My firebird (poncho 400 and th350) is shifting funny the last couple times ive driven it. it normally shifted around 2000 rpm's but now its shirting around 4000. checked and toped off the fluid, it was a little low but not bad. What shoudl i check next?

 

Vaccuum modulator.

 

Mine did that awhile back shifted fine and then all of a sudden wouldn't shift till about 4k and shifted hard. Vacuum line had come off of the transmission. hooked it back up worked fine. 1967 400 th400 firebird

 

Thanks, found the spot where the vacum line should be. Now just have to put ot back on i guess.