Why would the shaft between the transmission and transfer case need a slip joint? Both the transmission and the Spicer 23 should be mounted pretty solid to the frame. The slip joints should be installed in the driveshafts coming from the transfer case and going out to the drive axles because of the articulation of the springs and suspension.
You do need a slip joint because the engine is mounted in rubber, the frame flexes, and the relationship between transmission and transfer case will change.
It will be much easier to install if there is some slip.
If there is no slip there will be extra end thrust loads on the output bearing in the transmission and input bearing on the transfer case. this binding could also cause problems with the engine and transfer case mounts, and also transmit noise and vibration between the two, and to the frame if the transfer case is solidly mounted.
Grigg
