<VV> How a diff works?

James Davis jld@wk.net
Wed, 01 Dec 2004 19:00:57 -0600


Well, I agree.  The pinion on the pinion input shaft transmit the torque 
from the transmission to the ring gear.  The ring gear is bolted to the 
diff carrier.  The pinion gear shaft  in the carrier takes the carrier 
torque and transmit it to the pinion gears. And finally, the pinion gears 
transmit the torque to the two differential side gears.  It is the side 
gears that turn the axles.   There is a single tooth of the pinion gear 
that contacts each side gear.  If you double the number to pinions then you 
double the tooth contact area.  The side gears are considerable  larger 
(stronger) than the pinion gears.

Pinion gears usually shatter due to shock loading.  Most common is when one 
rear wheel has traction and the other does not.  The differential will 
apply the most torque to the wheel with the least traction.  This causes 
the slipping axle to rotate twice as fast as the carrier (engine 
speed).   When the slipping tire regains traction suddenly, the entire 
engine torque and inertia of  engine, clutch, flywheel, transmission and 
carrier is loaded on the wheels.  In a rear engine car with sticky tires, 
the tires do not break traction but the pinions shatter.
Jim Davis


  The At 06:25 PM 12/1/2004, Bill Elliott wrote:
>I'll try to explain... please on of the experts jump in to correct me if I 
>have this wrong.
>
>In a '66+ Corvair, the diff is the weakest point in the driveline.  (In 
>the earlier cars it's the trans itself)  When 'somethings gotta give', 
>this is usually it. The
>spyders are the little gears that transmit the torque within the diff... 
>the ring and pinion translate the power from one plane to another while 
>the spyders allow
>one wheel to turn faster than the other.
>
>These are very small, lightweight gears which do not handle shock loads 
>well. The 4 spyder modification doubles the number of gears. It is a 
>common mod
>for V8 cars, but is also not a bad idea for any diff while you have it apart.
>
>What I _don't_ know, though... is what becomes the next weakest link in 
>the driveline. And I hope I don't find that out....
>
>Bill
>
>
>On Wed, 1 Dec 2004 18:46:55 -0500, RKAT wrote:
>
> >I have heard of the 4 spyder diff. How does it work? What is it's
> >purpose?
>
> >Thanks!
>
> >Ron Tinkham