Al Drive shaft

[macx]

for a correct, very detailed explanation of
driveshaft harmonics/vibration, check out
the tech section, transmissions, on www.tccoa.com (by a Ford trans engineer,
no less) He says with 3.7 gears and deeper
(or very high speeds) the aluminum is necessary - something about harmonics
and less rotating mass, etc.

for very good discounts on gen Ford stuf, see www.fordpartsnetwork.com they're in
Georgetown TN, just NE of Memphis.