Posted by Dan Shockley on Thursday, March 15, 2007 at 14:02:06 :
In Reply to: Differentials, Lockers, etc. posted by Clint Dixon on Thursday, March 15, 2007 at 13:38:14 :
Junior,
Great descriptions! I would like to add a little description of how the automatic positive locking traction aiding device creates some of the weird handling effects that are commonly sited.
In any 4x4 without a center differential and with open differentials (or spools, or ARBs), during a turning manuveur, the rear tire average speed is equal to the front tire average speed. However, in a turn, the rear axle travels on a shorter arc than the front axle. This causes driveline binding and tire scrub. In a vehcile eqquiped with an automatic locker, this is worsened by the locker, particularly in a freewheel condition. In a freewheel condition, the outer tire accelerates "around" the outer arc, while the inside tire contues at the same speed as the average front tire speed (dictated by driveline rpm). This means that now the rear axle is traveling on a shorter arc than the front, AND the average tire speed is now greater! Wow. now we have compounding of speed disagreement and the amount of scrubbing required to avoid breakage increases.
Now enter a spool or selctable locker in the front (result is the same with another automatic locker, but they are never recommended for use in the front of a vehicle). In the above case, you have three choises to choose from as to where the scrub takes place and it will find the tire with the least traction to absorb the speed differential! In the case of the locked ARB (or spool), there are now only two choices, the rear inside tire or the front tire with the greatest traction.. So any front locker can exaggerate this issue of speed disagreement, and can make some of the normal side effect associated with automatic lockers seem worse - particularly if you have developed bad driving habits. Things like tire chirp, tire hop, and rough engagement become more frequent. Of course, this is true for any front locker and is why only lockers that have a true open (or low torque transfew limited slip) are recommended for the front.
I am not trying to advocate for either locker. Each one has its place, and as Clint says, the buyer should know what he is getting as to avoid suprises. Neither device is without compromise. Neither device absolves the driver of the need to be sensitive to the vehicle and drive intelligently.
Great information!
Dan