1992 Chevrolet Truck transmission shift's hard

Last night I noticed one of my cable loose(I think it is called the tv cable right by my air filter) so I went ahead a tighten it up well this morning when I'm heading to work right away my 1 and 2 gear both shifted hard I only live 5 minutes away from work so I didn't get to see if it got any better but it has never did that before. Ooo and I added half a quart of transmission oil in yesterday but when I drove it after that it was shifting fine any help would be very much appreciated