Jack up rear wheelS(both). Put in neutral w/emer. brake off. Have
someone hold one rear wheel still while you try to spin the opposite one.
If it spins ok, it's unlocked; if it is extremely difficult to turn, or will
not turn, it is locked.
Had an acquaintance lose his responsibility for ordering new cars when
he ordered all GMC 4X4's w/o specifying locked differentials. Perhaps even
a 2X w/posi-trac'n. differential will pull better than a 4X w/unlocked
It really depends on what you are doing. Limited slips don't create
traction. If both rear wheels are loaded the same and are on surfaces with
similar frictional characteristics, the limited slip isn't going to help
much. Now if one rear wheel is unloaded or in a mud hole and the other is on
firm ground, then a limited slip can save your ass. However, a limited slip
can make it easy to loose the rear end on low friction surfaces and spin out
the vehicle. Personally I'd never order a 4x4 without a limited slip rear
axle. On the other hand, in 40 years of driving farm tractors with locking
rear axles, I've never once had locking the rear axle get me out of a jam.
The usual result of locking the rear axle is burying the tractor to the axle
housing. But this is a situation where both wheel usually have the same
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