95 1500 Trans problem

I have a '95 GMC 1500 V8 5.7l. Ihave 2 problems ( Ithink that is the transmision).First when it shifts from 1st to 2nd gear it does it really rough, like somebody hit me from the back. And second I just installed a throttle body spacer and now when I idle at 1500-1600RPM and accelerate a little bit it downshifts and upshifts right away. I searched online to see what is the problem and I found out that I have to adjust the kick down cable, but I do not have a kick down cable.
Can anyone tell me what is the problem and how can I fix it?
Thanx a lot