I had to replace my ride height arms on both sides in the back of mower. Now the mower will not roll backwards freely while running. I made sure the little springs and woodruff keys are in place on the drive gears, and they are greased. The bar that you push to engage the transmission engages when you push the bar about 1/2 way forward. The spring on the transmission seems to allow the arm on the transmission to return to the normal position, meaning the transmission is not engaged when the bar is in the back resting position. It seems like the mower can be rolled backwards right after starting the mower, but some tension can be felt. The longer the mower runs, the harder it is to pull the mower backwards. After a few minutes, the wheels will lock up when rolled backwards, but will roll freely forward. The mower rolls forward fine when the transmission is engaged also. Any help would be appreciated.