Weird 4x4 open diff/posi diff question? Please read

[Patsfan34]

So I guess my assumptions may be wrong sometimes. My dad (who had a 68 1/2ton 4x4 back in the day) was telling me that all 4x4s have posi-traction in both the front and rear. The frame i'm using is a 68 GMC 4x4 1/2 and I thought I was told it's an open rear end. Can you guys please tell me what's what? Explain it like I'm 12 years old so I can clearly show it to my dad, whether he's right or wrong.
Thanks,

Patsy

[Stocker]

There must be some sort of misunderstanding, or something was lost in the translation....

My 4x4, like a great many others, has open differentials front & rear.

Many others have posi-traction (GM's name for its limited-slip) in the rear diff, but factory installed limited-slip *in front differentials* are rare at best.

One feature of a typical AWD vehicle is an open center differential (between the front & rear axles) which -- in some cases -- can be locked. True 4WD vehicles, such as our old trucks, have a transfer case which can lock the front & rear axles together with no differential action.


Edit: to determine if you have an open diff or limited-slip, park the truck on level ground and chock the front tires. Release the parking brake and put the truck in neutral. Jack up the truck until the rear tires are off the ground. By hand, rotate one rear tire and observe the tire at the opposite end of the axle. If it turns in the opposite direction as the one you are turning, you have an open differential on that axle. If it turns in the same direction, you have a limited-slip.

You can check the front differential the same way, by chocking the rear tires and jacking up the front and rotating a front tire.

[LONGHAIR]

Like Stocker said, "posi-traction" is an option, so it's anybodies guess as the what truck may have it in the rear.
I have heard "talk" of factory installed posi front axles. People have even said that they have seen SPID labels that show the option in the front....but I have never seen one in person.

[andyh1956]

i bought a bronco new in '75 & had l/s in both ends. dana trac lock in the front & whatever ford called their "almost non existant" locking rear diff stuff. anyway front & rear l/s were both "extra cost" options. oh yeah it's worth whatever they cost! (don't spend any $ on oem ford stuff, get something better)
andy

[Patsfan34]

Thanks guys!