speedo cable?????

when i got my car the speed o did not work. i found out the cable was wrong and was not attached to the speedo. it was the screw on type and the guage was snap on. so i got a snap on one and hooked up to the 4 speed and guage. now it reads like 80 when parked and goes up to 110? when going at all. it bent the needle. so i disconected it and turned the cable till it read 0mph and hooked it back up. it just went back to 110 or whatever the fastest it can go. could it be a bad guage or what? i have a spare guage so i can put that in if you all think that could be it. i probably will have to anyways cuz of the bent needle