Differentials allow shafts to spin at different speeds - hence the name DIFFERENTial. Axle differentials allow the axle shafts to spin at different speeds which allows the inner tire to spin at a different speed than the outer tire in a turn. If the axle was a single shaft then turning would not be possible without tire slippage - which doesn't happen on asphalt. The axle would break. When you put your truck into "4X4" mode, what you are doing is locking the front and rear drive shafts together, you are NOT locking your front - or rear - tires together.Some full time four wheel drive vehicles run with a central differential that workskinda like your axle differentials and allows the front and rear driveshafts to spin at different speeds. However, most truck 4X4 systems have only diffs in the axles and when the truck is put into 4-wheel drive the front and rear axles are locked together and must spin atthe same rotational speed. The axle diffs allow the tires to turn at different speeds. When turning, the front and rear tires cover different distances and if you're on pavementitcauses extreme distress to your transfer case as the axles attempt to spin at different speeds. It will even happen going straight after awhile if there is any difference in tire pressures, and as a result tire radius, since this will also cause the front and rear tires to spin at different speeds. Eventually the transfer case will explode under the stress of the situation.

I hope that was understandable[&:]

 

The following is a Cut & Paste from the Jeep website:

"The Quadra-Trac II 4 x 4 system gives owners the benefit of the NV245 active transfer case and BTCS. The transfer case is the same one used in the Quadra-Drive II system. When activated power is delivered only to the rear wheels as it takes input from a variety of sensors to determine tire slip at the earliest possible moment and take corrective action. The system also uses Throttle Anticipate – sensing quick movement in throttle from a stop – and it takes steps to maximize traction before tire slippage even occurs.
Torque is transferred to any of the four individual wheels as needed by the BTCS to maintain traction in changing road conditions. When the system senses tire slip, it modulates brake pressure to the slipping wheel, which directs torque to the tires with the best traction."

Which is pretty much what I was attempting to describe. Which is why he could drive on dry pavement so much easier and without risk of component failure with his Jeep's 4 Wheel Drive System.

 

also some jeeps have a full time transfer case that can be put into 2wd- 4wd (full time)- 4wd (part time)- 4wd low (part time)
basically its like having another differential in you transfer case when in full time 4wd
the part time locks the front and rear drive shafts like what we have in our trucks

 

Yep, I know that's what you were talking about. The NV245 active transfer case is essentially a central diff, as I explained above. I was just trying to help him understand howfour wheel drive systems worked in general.

 

"... and if you keep using your 4x4 system on dry pavment.. your gonna break somtin.... "

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