flaco

Hello....I installed a new after market wiper transmission yesterday...I bolted the original motor back in ( was working perfectly)...When i turned it on it was frozen...I started to take the motor off and when it was loosened the transmission began turning the posts...as i tightened it back the transmission stopped turning....Seemed only to work when the motor was loose and wobbling on the firewall...All my 50 years of driving i have never replaced a motor and a transmission....anybody have any experience? thanks, Jeff