repo speedometer issues

[cameyer]

I just put in a new speedometer from classic parts for my 64 k10 and the thing does not seem to work worth a damn. I have tried 3 different speedometer cable (the original one, regreased it still didn't work, a new one to the transfer case, still didn't work, and a new one to the transmission, still didn't work). Here is the issue the odometer works and is close enough correct to an exact mile but the speedometer needle goes crazy. it wont even register unless you are going down the freeway and if you hit any bump will drop to zero then back again and if you take a turn to the left speed increases about 20 mph and a turn to the left speed drops 20 mph. Any one have any idea what is going on?