Let's pretend through this example that you have 3.73 gears.
If you have a locker or good traction (or even a limited slip with equal resistance on either wheel), then when you turn the driveshaft 3.73 full turns, both wheels will rotate one full turn. That's the gear reduction at work.
Is that not what we are talking about???????????????
Now, pretend you're making a tight turn, where the outer wheel has to turn more times than the inner wheel to complete the turn. Because of the way an open differential works, when one wheel turns slower than the ring gear, the other wheel has to compensate by turning faster than the ring gear.
In this situation, for every 3.73 turns of your driveshaft, the inner wheel may only make half a revolution, while the outer wheel makes 1.5 revolutions.
Basically, for each 3.73 turns of the driveshaft, there must be two full wheel turns for the two wheels combined. When driving a straight line, each wheel makes one full turn. When turning, one wheel may make 0.8 turns while the other makes 1.2 turns. The tighter the turn, the more dramatic the difference between how fast the two wheels turn.
DUUUUUUHHHHH. That is why it is open until the LSD locks up. Wow, this guy is John Madden--stating the obvious.
This situation is exaggerated when you jack up only one rear wheel while leaving the other on the ground. One wheel cannot rotate at all, so the other wheel (the one you're turning) must make two full turns in order to get one full rotation of the ring gear in the differential. One rotation of the ring gear will generate 3.73 rotations of the pinion gear.
If you jack up both tires and leave the tranny in gear, the ring gear won't be allowed to rotate at all. Therefore, if you jack up both wheels and try to rotate one of them (with an open diff), the opposite wheel will have to rotate the same number of times, but in the opposite direction. If you try this trick with a good limited slip, you'll have to really wrestle the tire in order to get it to turn, since you're trying to overcome the slip-limiting force of your LSD. If you try this trick with a locker, you'll pop a blood vessel before you get the tire to turn, since a locker won't let either wheel rotate without the driveshaft turning. That's the whole point of a locker.
So, assuming you've got an axle up in the air with the driveshaft disconnected
(or the tranny in NEUTRAL) & neither wheel on the ground:
- If you turn one tire & the other one either stays still while the pinion rotates, or the other one rotates backward while the pinion stays still, or something in between, then you've got an open diff or a very weak LSD (like a Trac-Lok with too many miles on it). In this case, you need to secure one wheel (perhaps by lowering the tire onto the ground), then you can figure your gear ratio by rotating the airborne tire TWO full rotations and counting the number of times the pinion rotates. 3.73 turns means 3.73 gears. If you only rotate the tire once, then 1.865 turns means 3.73 gears.
- If you turn one tire & the other one turns the same number of turns in the same direction, then you've got a good LSD or locker. In this case, you can just rotate the tires ONE full rotation and figure your gear ratio by counting the number of times your pinion rotates. 3.73 turns means 3.73 gears.
2000 Silverado ECSB- 5.3 CAI, Pacesetter LTs, ORY- Pipe, Magnaflow XL, E-fan, Ported T/B , Nelson Tuned, Built 4l60e, Circle D Stall, 3.42s G80, 2-4 Drop, Hertz Highs, Rockford 501s
Originally Posted by LamboDoNoMo
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