motrctyman said:
I'm trying to remember, but I don't think that both wheels should have spun (they will spin, but not like direct driven, if that makes sense). There is an electric acutator in the front axle that "extends" when the t-case is engaged in 4hi/lo. Which will lock both front wheels together and make it very difficult to go around corners (much like Blueruck mentioned). If you can coast around a corner at 5-10MPH without coming to a stop, then your not engaged.
Your memory is close, but I think it is just a little off.
We had a discussion about the inner workings of the front differential a little while back:
Help Me Understand My Avalanche.
The actuator to which you are referring to locks the front half-shafts (the ones between the differential and the wheels) to the pinions in the differential, but they do not lock the two front wheels together. The front differential is always open. The actuator "locking" the front half shafts is only allowing power to be transmittied to the wheels, the front wheels are always able to turn at different speeds (as they must when going around a turn.) This "locking" of the half shafts to the differential is the equivalent of "locking the hubs" on older 4WD systems, where you used to have to get out of the truck and turn the locks on the front hubs to engage 4WD. Similar concept, with the biggest difference being which end of the half shaft has the lock.
Still, you are correct that if the 4WD system is engaged, you will still bind up the tires going around a corner on dry pavement. Not because the front diff is locked, but because the transfer case is locked (no differential or slipping in there) so that the front and rear drive shafts must be at the same speed, but they are trying to turn at different speeds through the turn. (That's a really bad explanation, but I hope you know what I mean.)
In the thread above, marc_w brings up a good point: there is enough drag in the transfer case and front axle, that even when everything is disengaged, the drive shafts may still be spinning (but with no power.) Even if you try to spin it by hand, you may still get the wheels to turn from the internal drag. However, while spinning the shaft, you should probably be able to stop the wheels by hand and prove that things are not engaged.
I'm tired and I need to go to bed. I'm re-reading what I'm writing here, and it doesn't seem very coherant. Hopefully you can get what I'm saying. I'm afraid I'm going to read this in the morning and say "what was I thinking?)
-- SS
