question about transmission if failed or not

[rbtunner]

alright so i had the tow guy tow my 90 240sx with sr20det cause of a bad head gasket, but i noticed that when he took the car off the flat bed trailer he left it in gear one and when the car was rolling backwards off you can see it like sorta moving backwards uncomfortably. but after he took off that is when i noticed it in gear one. i put in a new head gasket, new clutch, and now when i drive the car i can shift into all gears smoothly but in every gear it moves freakin slow like barley. i have to rev the car up high to get it moving. almost feels like the clutch is slipping but its got a brand new XCT clutch and installed it correctly i took it off and double checked to make sure. Do you think the transmission is messed up????? Any opinions would be highly appreciated. thanks