Pretty new to this. I have a 1991 Ranger XLT 4x4. 2.9 engine. Pretty stock except for a 3" lift and bigger wheels/tires. Here is my question before I head into mud and sand: even in 4 wheel drive, in very slippery situations like mud and sand, only one front wheel and one rear wheel will spin, right? I mean, the stock vehicle doesn't have lockers, right? and what about posi? Nothing on the front or rear stock? I watched while a brake job was being done, and they spun one rear wheel and the other didn't spin with it... I want to drive the truck out in the dunes, but I'm really worried about getting stuck while 3 hrs from home and no one around.

 

According to Edmunds.com, the '91 XLT Ranger had an optional LSD rear diff. Now to know if yours has it or not, check on the diff itself, you should see a metal plate with indications as to diff type and gears

 

Look on the drivers door edge for the Safety Standard Cert. Label
There will be an AXLE code number like 87 or R6

Go here to look up Ranger axle code: Ford 7.5 & 8.8 Inch Axle Tag & Door Codes

Open = standard axle(only 1 wheel spins)
L/S - Limited slip(both wheels spin if you get stuck, lol)

Limited-slip differential is the generic name, posi-traction is what GM calls their limited slip differential.

There are also locking differentials, these have a selectable "control" that physically locks the differential so both axles spin at the same speed, great for traction but bad for going around a corner on a hard surface.

L/S is a compromise between open and locked differential

Front axle/differential will be the open type no matter what rear is, but it will have the same ratio as the rear, i.e. 4.10, 3.73, ect.....


Lowering tire pressure is a must in the sand, you need a wider softer footprint to stay on top of the sand.
So a portable air compressor or an air tank is handy to have, so you can refill tires and make it to the closest "real" air compressor.
Also in the Oregon Dunes parks a red flag 9ft above the ground is required on all vehicles.
And I believe you need a permit now as well.