Okay, now I'm confused. I always thought that by engaging 4wd on a Wrangler, that it "locked" all four wheels together. Isn't this why it is called a part-time 4wd system, as opposed to full time? If the wheels weren't locked when engaged in 4wd, then why are owners urged to only engage 4wd on slippery surfaces where the faster wheel can slip (loose traction) to stay in sync with the slower wheel such as in a turn, and warned that if driven on dry pavement the wheels will hop and chirp because they can't turn at different speeds, thereby "binding" the differentials?? Because of this, I always though it ws a true 4x4. What am I missing?? Also, I always thought a LD was best on dry pavement in a 2wd situation, since off-road, it won't work if one wheel is in the air. Finally, since part-time lockers are obviously best (I know I'm wrong, I just don't know why), why won't the manual Warn locking hubs fit on the axles of the Wrangler (TJ & JK) when they fit on the older CJ? Thanks for any and all clarification of my confusion.
Four wheel drive "locks" the transfer case and sends 50% of the engine's torque to the rear driveshaft and 50% to the front driveshaft. From there, it is transfered through the differentials in the axles to the wheels. The way that differentials work is they send the same amount of torque to each wheel, but they send the amount of least resistance. So when you have a wheel in the air, it doesn't take much torque to turn it, so that is how much the other wheel gets as well, that is why you will just spin the one in the air, while the other stays stuck in the mud (or behind the rock, or in the snobank, etc.
). The reason for this is when you turn, your wheels follow a different path, and therefore, different distances.
The reason that you hear "chirping" when driving in part time 4wd on pavement is that the drivetrain binds as all the wheels are turning at different speeds during a turn and the transfer case is trying to turn the front and rear at the same speed. This causes binding in the drivetrain, and if severe enough, will unload on pavement, spinning or stopping tires and causing the "chirping" that you hear. That is why it is called a "part time" system, as opposed to a full time system which has a differential type transfer case allowing the front and rear axles to spin at different speeds to avoid driveline binding. The full time systems are often very similar to "all wheel drive" that you find in cars.
The hubs won't fit on the YJ's or TJ's because the bolt pattern on the wheels is smaller and won't allow enough room for the regular or premium hubs that Warn makes. They do (or did) make a kit specifically for the 5 on 4.5" bolt pattern that the TJ's and YJ's have. The TJ's use a solid "hub" system that has the front axle shafts (and driveshaft) spinning all the time, and the YJ's use a vacuum disconnect system to disconnect the front "hubs".
I think that covers everything, but it may confuse you more than help. Feel free to ask any clarifying questions without fear of flaming. I haven't even read the whole thing at once yet, and it may get a major edit in the future, but should be a start.