I jacked my rear end today with the other tire still on the ground. I spun the wheel and the drive shaft turned. Is there something I'm not seeing?

 

sounds like an open rear end to me. if it was posi, you would have turned both tires or not been able to turn just one.

 

I believe that a clutched rear end will act like that. I may be mistaken but as I recall, if you lift the entire rear end and spin one wheel in a forward motion, the other wheel will turn in the same direction if posi. If the other wheel turns the opposite way, then it is not posi.
I was told this a long time ago and am not sure of the validity. I do know that most of the mid 70's ford f250 4x's were supposed to come with limited slip / posi in the rear.
I too am curious so if any of you diff girus out there have additional input, please step in.

 

the drive shaft will turn no matter what. what the other wheel does is what tells you.

 

1st off welcome to FTE!!

What were the front tire's doing? J/K

You would havre an open rear end, if it was a posi rear end you would not of been able to turn the tire as the other one on the ground would have prevented that.

You would be correct olfordsnstone, a posi will spin the same way as the other wheel is being turned provided the other side cannot be held back, meaning both wheel's will turn equally. If you have a buddy hold the other side from turning and your side does turn it is a limited slip.

 

how do you tell if it is a limited slip or open ended? and what is open ended? If the differential is open ended, why would they put that on a 4 x 4 ?

 

Not sure of the term "open ended" but the term I use for non-limited slip is "one legged". This would mean that one of the wheels is the drive wheel on the rear. The same would apply if one legged in the front. Limited slip means that if a drive wheel begins to loose traction and spins, the other side would kick in and assume as drive wheel. This gives a walking action with the wheels taking turns at drive wheel.
The reason they do this is for slippery road conditions like snow. The wheel that is not performing as the drive wheel keeps the rear end from slipping from side to side, or gives lateral traction so to speak. A true posi rear end, meaning both wheels acting as drive wheels together, is good for climbing and mud bogging but not so great for road use in slippery road conditions.
This topic came up in earlier threads and Torque 1st had some good info on air locker rear ends. These are one legged rear ends but can lock the rear end into a true posi with a flip of a switch or something. I will be looking for one of these when I get to that part of my project truck.
The typical rear end in the mid 70's f250 4x4's are limited slip. As long as the clutches in these rear ends are still in good shape, they seem to perform very well. I believe the front ends came from the factory as one legged.
I wish I could answer the question on the open end term. Might be the same as one legged???? Hope this helps though.

 

This thread probably belongs in the section for axles. I have not used the terms "open ended" or "one legged." To me, an "open" differential is a simple basic differential. It has a ring, a pinion, a pair of side gears, and a pair of spider gears. It was created to allow vehicles to go around corners without skidding tires or going off the road. It allows the two driven wheels to turn at just about any variation of speed in relation to each other, including " driveshaft and speedometer showing 20 mph, while one rear wheel sits still and the other turns at 40 mph."

A limited slip has a pack of friction clutches that allows some difference when going around a corner, but strongly resists a big difference in speed between the two sides.

Lockers use mechanical means to lock up the normal differential action. The effect of a big difference in speed between the two sides is to operate the locking mechanism. The locker in my Suburban will usually operate after the wheel with bad traction makes about one turn. After that, the two turn together. It will unlock when it unloads.

There are also manual lockers, like the aftermarket ARB and the axle lockers available on large trucks. For the most part, though, the manufacturers' liability lawyers believe American drivers are too stupid to be trusted with manually locking axles (they'll leave 'em engaged when trying to turn a corner on the street, then sue after they go off the road).

I don't know if my "locker" will let me turn one tire with the other side on the ground -- I think so, as I've never noticed otherwise, but I am usually interested in NOT turning the wheels while I'm mounting tires/wheels. I'll pay attention next time I rotate tires.