1970 Monte Carlo assembly line photos

[Kurt S]

Originally Posted by Keith Seymore

You may already know but that is to control rear axle whine (as a result of "non conjugal meshing action" of the ring an pinion).

We used a lot of those on the old Astro/Safari vans, and on GMT400 pickups with the aluminum one piece shafts.

Why is it only a problem on some carlines? Is it an axle design issue or something else?

[Keith Seymore]

Originally Posted by Kurt S

Why is it only a problem on some carlines? Is it an axle design issue or something else?

Usually it has to do with the interior volume. Vehicles like vans or Suburbans are particularly sensitive to all kinds of disturbances, since the body cavity can respond like a drum. An axle that would be ok in one vehicle would be "bad" in one of those.

The other consideration is if the "noise transmission path" is through the structure or is airborne in nature. Normally it finds its way into the vehicle through the rear suspension (you can actually detach the rear suspension and run the vehicle on a chassis roll dynamometer to verify the noise goes away). That is what was unique about the GMT400 project is that the noise would radiate off the drive shaft and was airborne - if you were standing outside the vehicle you could hear the axle whine as the truck drove by...

K