powerglide won't shift

Question : I have a 1968 Impala SS with a 327 and a powerglide. The transmission had the pan pulled (hardly any band-friction material in it)and a mild shift-kit installed. Although 1st,park and reverse are fine, the transmission won't shift into second and acts like it's locked into 1st (engine breaking on deceleration). The shifter and TVS linkages are adjusted properly and the vaccum-modulator "appears" to be OK.
Any help you could provide would be GREATLY appreciated. Thanks in advance for your time.

I wish I had answers but mine does the same thing. Full throttle manual upshifts feel like it's going into neutral until you let off the gas, then it usually goes into second in a few seconds! Only sometimes though! (Not good) I had a manual valvebody and a shift kit put in.... Still the same.... I'm thinking there's something more major wrong....

Anyway, make sure your modulator is hooked to the right vacuum source. Also, I think by adjusting the downshift linkage, it changes the timing of the shifts.... Just some ideas.. Good luck!

I'm not familiar with Chevy products, but is there a band adjustment you can do on the outside of the tranny? I know with my Ford C6 there is.