Re: Haldex

["Matt Rooke" <mrooke@fcpa.fujitsu.com>]

I'm suprised there haven't been a bunch of very informed technical posts on this, so I'll just
relate the superficial stuff I've gotten from car mags.  But even this level of info was enough
for me to form an opinion.
The Haldex system employs an electronically activated clutch.  Under normal conditions,
"nearly all" of the torque goes to the front wheels.  When wheelslip is detected, the clutch
engages and sends increasing amounts of torque to the rear.  I don't remember what the
max. percent of torque can be shifted.  The promotional literature brags about how very
few degrees of wheelslip is all that is needed to engage the system.
Hence, Phils comment that the Haldex is a part-time system.  I think Audi is doing themselves
a dis-service by conferring the "quattro" label on this system (I know, some urq purists
feel this way about Torsen).

The driving reviews I've read stated that the torque shift to the rear could be felt.  In an
attempt to be optimistic, they use phrases like "could barely be detected".  But you don't
see that in reviews of Torsen systems.

Thanks anyhow, but I want a system that drives all 4 wheels all the time.  Shifting torque around
the way the Haldex does, seems to me to detract from stability, rather than enhance it. (I know,
there are some situations that have been described where sudden shifts can occur with a
Torsen when being driven at 10/10).   For me, the Torsen systems, esp. the new ones with
f/r EDL (for getting un-stuck), are the right prescription.

But if someone will loan me a TTq for a few weeks, I'll happily try it out objectively ;-)

Matt Rooke
'91cq- torsen, manual rear diff lock