Has it ALWAYS been like that or did it just start doing it??

 

I am having a similar problem...
(I have exchanged posts with you guys over the last three years, thanks for all the help): 75 Camaro, just put in a rebuilt 350 in place of a straight six. Car has a TH 350. Car kicks/drags when going through gears, and is apparently shifting way too fast- a transmission shop told me that my vacuum pressure is way too high, and showed me how it shifts way too quick into 2nd and 3rd. He also reconnected a vacuum line which he said was in the wrong place.
I drove the engine in another car before I put it in my car, and I'm sure that it is not getting all the engine's power. I also realized my TV cable (kick down cable?) basically doesn't fit (from the old engine set up) and is not in full use- I will be getting this fixed soon as possible....shop seemed to think this would not solve the full issue though. Any help is greatly appreciated! Sorry for long post, thanks again.

 

I think your shop is wrong on the TVR cable. It's coonection to the carb, and correct adj. will definitely affect trans shifting. If the cable is fully extended all the time your trans will not shift until extremely high rpm. If it's never extended the trans will shift too early.
Get it set correctly and it will shift at the coorrect point if everything else is good.

 

Yes, the cable does play a part in up-shifts, in conjunction with the vacuum modulator and governor.
Speaking of the modulator, what vacuum source do you have it connected to?