Slide off what? I have never removed one from the top through the cab. Out the bottom allows much more room.
If you have the bell off of the back of the transmission, you have to disconnect the U-joint held by four bolts and the shift linkage along with anything else connected to transmission, like the speedometer cable. You might have to remove the crossmemeber to allow the drive shaft to fall below the transmission and allow enough room to take the transmission out. After the above is done, unbolt it and pull it back until the input shaft clears the bell housing, then lower it. If you are going out through the top, it seems that you would have to remove the seat and the floor covering and roll it out the door of the cab. I like the bottom better.
Good luck!
