jpony645 said:
Falcon: I understand that. What I'm trying to figure out is how does "part time" 4wd work on it. Is it like traction control where the computer sends more power to one wheel or another when it loses traction?
First PT: The transmission turns the input shaft of the TC. The turning is directly transfered to both front and rear driveshafts. If the input turns one turn, both the front and rear will turn exactly one turn. If you are on snow, ice, gravel, anything that will allow the wheels to slip a little, everything is cool.
However if you are on asphalt or similar, there is a problem. For a variety of resons such as turns, uneven inflation, tire size etc. the front and rear will want to take a different number of turns and when they can't, loads build up between the front and rear.
What would happen between the left and right side of an axle with no differential, happens between the front and rear axles because there is no differential in the PT position.
This means that you can be in PT position only when driving on ground that "gives", not all the time. (Part Time)
Thransfer cases with FT position add a differential between front and rear outputs.
One turn of the transmission depending on conditions, will mean a little more on one end and a little less on the other, as needed. Just like your rear axle does between left and right, no difference.
The transfer case differential looks a little different than a standard rear end differential, but it does the exact same thing.
Because of the differential between the front and rear output, you can use the FT any time any place with no worry that you are stressing the drive system.
Your next question might be why you need PT at all.
There are times when you can't get good traction because either end is slipping like crazy using all the power with the other end doing nothing.
In that case PT can save the day because it will force both front and rear to turn equally.