Join Date: Sep 1999
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Re: transfer cases
Basically, Command Trac is a part time 4wd system, meaning that the transfer case locks the front and rear drive shafts together and they will always turn at the same speed. Some of the Command Transfercases are the NP 207 and the NP 231. Command trac 4wd should not be used on dry pavement or other high traction surfaces.
Select Trac is a full time 4wd system, which means that there is a differential action of some kind in the transfercase, allowing the front and rear driveshafts to turn at different speeds, somewhat like an open differential axle in a turn; the tires can turn at different speeds removing strain on the drive line. For this reason, Select Trac systems can be driven in 4wd on the pavement without damage to the transfrcase. Some Select Trac cases are: NP228, NP 229, NP 242 and 249. The 242 case also has a part time 4wd mode. [img]/wwwthreads_images/icons/smile.gif[/img]