I just replaced my front differential on my pickup. When the truck is in 2 wheel drive, is the propshaft from the transfer case to the front diff still supposed to spin? I'm still concerned that my truck may be trying to engage in 4wd on its own (it's a push button switch on the dash, not a manual on the floor) and I may still need to replace the 4x4 actuator. Or should the shaft only spin when the truck is in 4wd.