Rear differential

[1980 Bu Baby]

If my rear end is worn and in need of a rebuild to my understanding it will act as if it is an open diff meaning if I jack up the rear and rotate one wheel the opposite wheel will rotate in the opposite direction. If this is the case do I calculate the rear gear ratio like an open diff at this point or like a typical LSD. Problem is the person I bought my car from told me the rear was a LSD with 4.56 gears so I jacked the rear of the car up and rotated a wheel and counted the driveshaft revolutions and it spun roughly 4.5 times but it is possible it has always been an open diff and that would mean my method is inaccurate considering how an open diff works. I know this is confusing but I can save a boat load of time if this is a real 4.56 rear that's just work out.

Thanks in advance.

 

[bracketchev1221]

The tires will spin opposite if the trans is in park. But if in neutral a good posi SHOULD spin together. But look at it this way. Worst case is, its a reason to pull the cover and change the gear oil .

 

[lilbowtie]

You might have a gov lock posi in which case it is hard to tell w/o looking. If you turn both tires at the same time then you can count drive shaft rev's. If you hold one tire the other will spin twice as fast due to the spider gears.