Auto Transfer case operation

[rhsub]

My 99 K 2500 sub has a auto transfer case #246, does anybody know if itis normal that the front driveshaft turns all the time, its not hooked up solid (I can turn it by hand) but it seems to have excessive drag on it, enough that its driving the front diff at full speed (and wasting expensive fuel), Has anyone switched one to a non auto electric shift case, I don't use the auto feature, Don.t care for it much. I don't really want to go to the manual shift if I can help it, I like having the open transmission hump area.
Thanks in advance
Ron

[Dimsdale]

The driveshaft should only turn when the transfer case is in AUTO or one of the 4WD settings. In 2HI, it should not turn with the front wheels (the disconnect of one of the halfshafts only allows the other to turn the spider gears in the differential).

The electric shift mechanism should be trouble free assuming it is working. It helps to be rolling slightly when shifting. The encoder motor is what shifts the gears, but the axle engagement solenoid is mounted on the axle.. I would make sure the connections on both is good and clean and packed with dielectric grease.

A synthetic oil in the diffs can reduce drag.

One thing that the AUTO feature does allow you to do, that the non-autos don't is that you can engage it periodically in the summer to distribute the diff oil through the gears and warm it up. Perhaps that is not necessary anymore, but the monthly engagement of the front end is something that you used to have to do if you had free wheeling hubs. It can't hurt!

[DmaxMaverick]

If you have a NP/NVG 246 "Autotrac" transfercase, slight friction (you should be able to overcome the friction by hand) is normal on the front shaft. The parasitic drain is insignificant, so your economy won't be any different than an electric shift or manual shift TC, if not operated in the auto mode. The auto mode can decrease economy slightly, though. The friction you feel is from the slight clutch engagement w/in the TC. Be sure to use Autotrac II fluid when servicing it.

You can switch it over to a manual or electrically operated (push button) TC if you wish, but the expense and effort will absorb any gains you may see. The Autotrac system is normally very reliable and trouble free, comparable to the service life of any other TC. They are more expensive to repair, however.