RE: alfa-digest V7 #507

["Brad Harris" <brad.harris@domain.elided>]

I am not saying that tired rear springs could not cause the same problem I
was having, but in my Alfa this was not the case. The car was only 4 years
old at the time and the rear sat within factory height recommendations. The
slapping would also happen on the highway when ever I would hit an expansion
joint with constant torque on the drive shaft. Once I replaced the
transmission mount I never had another problem. I drove the car this way for
over 30k miles (with the same springs) without any thumping. I finally
replaced the springs with Shankle Super Sport springs. I can't say this
helped the movement in the driveshaft because I was having no thumping
before I put the springs in.

Tired rear springs may cause the same thumping but based on my experience,
that was not the cause of my problem.

Thanks,

Brad H.

- -----Original Message-----

In my experience, the most common cause for the dreaded driveshaft
thump is tired rear springs. When the springs are partially collapsed,
the driveshaft is working at an angle, with the bend in the middle, at
the first U-joint, just behind the center support. The torque reaction
on takeoff causes the driveshaft to want to push up where the bend is,
hence the "thump". Replace those springs, preferably with something that
makes the car handle a little bit better at the same time.

Joel Hailey
Centerline Products
Boulder CO
303-447-0239

------------------------------