Differential underdrive

[Brandon505]

I heard that in typical rwd vehicles the drive-shaft rotates about 3 times faster than the drive wheels using gear reduction in the differential. Do most
trans-axles do this too?

[Brandon505]

the differential in the trans-axle i mean

[Dave B.]

Originally Posted by Brandon505

I heard that in typical rwd vehicles the drive-shaft rotates about 3 times faster than the drive wheels using gear reduction in the differential. Do most trans-axles do this too?
the differential in the trans-axle i mean

Yes. The only real difference is that in a FWD car, the transaxle bolts directly to the engine, eliminating the drive shaft. All the rest of the mechanical operations are very similar.

DB

[JoeDeJong]

Even in a front wheel drive there is a differential and substantial gear reduction. Times change, however. For example in the late 60's and 70's and even into the 90's it was believed that a lower mechanical advantage would give better overall results. But they coupled these 2.47:1 - 3.00:1 ring and pinions with heavy cars and it caused an insatiable apatite for fuel consumption. What we have learned since then is that your driveline soaks a lot of energy in the form of torque loss, which is alleviated by higher RPM's and more mechanical advantage to the closest point where the vehicle is applying power (the road). So there is a balance. To find the highest mechanical advantage where torque is lost the least, and where friction from higher RPM's become a factor. And this friction is an inbalance in the drive shaft, or heavy gear oils, etc.