[msdz]

Full time 4WD is considered the "dummy" 4WD around here. Full time 4WD is the SAME as part-time 4WD only difference is no driver input is needed. No need to turn hubs in or out. No need to make a transfer case selection. If a vehicle is labelled as part time then what it usually means is the transfer case is disengaged OR the hubs and transfer case is disengaged OR driver has to disengage hubs manually and transfer case is disengaged which improves MPG. A transfer case is engaged or it isn't, if it is in between then you have problems and need to get it fixed. A transfer case does not allow one wheel to spin faster or slower then the others, that is all in the differentials. Lets say you have a TRUE 4WD and the diffs are "LOCKED" together, then you would not be able to turn to good and also cause a lot of strain on your inner axles possibly causing them to break. Even the Detroit lockers you can buy and have put in your diffs have to have a little bit of slippage or eventually you are going to snap your axle(s). ARB air lockers have very little slippage or none at all but can be engaged and disengaged. Also without the diffs in a vehicle or having a "solid" axle your tires are going to wear more when you go around curves. I know a lot of people that have used Detroit lockers and do not like them cause if they fail to allow the slippage they say it isn't long before the axle snaps. I have a '94 JGC Limited and it is full time 4WD and everything spins just the same as a part-time 4WD and take it mudding as I would any other vehicle, I have only options on transfer selector for Full Time 4WD, neutral, and Low Range 4WD. Of course I have never seen a cause for using low range YET. I go mudding, not rock crawling.

At certain highway speeds a full-time transfer case may release allowing better MPG though. I have had mine up to 85 MPH when stuck in a mud hole and my front left and right rear(sometimes the left rear would spin also) were still spinning. Part-time can also be ran on the highway if you need it and don't mind the MPG.