Repairs hrb 215 sxa 2 speed

just installed a new transmission because the bearing for the gear the pulley is attached to was bad, the drive wheels moved but had very little power, after installing the new transmission, there still is very little power to the wheels,it acts just like the old transmision did, Question ; how much power should be at the wheels?, if I lift the deck up the wheels move fine,when I drop it down it does not have a enough power to even move the mower on a flat concrete surface, I have adjusted the cables per the manual, and the belt is not slipping,,any ideas anybody???? Thanks

Repairs hrb 215 sxa 2 speed