A few questions on my new A4

[Henry A Harper III]

> Hi guys, a few more questions:
>
> Per previous post, Just bought a '98 2.8L A4 5spd.
>
> 1. I read online that this car has the tosen diffs with electronic diff
> locks. How hard is it to install a manual bypass for these? I LOVE the
> ability of my 4000Q to manually lock diffs - makes the car hella
> more fun on gravel. And before I get lectured on it - yes I know the
dangers
> of driving on pavement with locked diffs.

The term "electronic diff lock" as used here is something of a misnomer. Or
it isn't what you are thinking it might be. Instead of an electronic means
to actuate a physical lever on the diff that locks/unlocks it, the EDL uses
ABS sensors to detect wheelspin across an axle and the ABS pump to actuate
the brake on the spinning wheel. On a 2WD car it's just called "traction
control". This is cheaper than a physically locking diff (see Daimler & BMW
AWD implementations for more examples). Unless there is a button on the dash
to turn it off like there sometimes is for stability control (ESP), you
won't be able to "manually bypass" the EDL - and that would turn them off
(leaving you with open F+R diffs) anyway so it's not what you'd be looking
for. I think EDL also stops working above a speed like 30mph, like the later
vacuum-operated lockers, but there probably isn't one wire to snip under the
back seat to override that - it's likely buried in the ABS brains.

In summary, EDL advantages:
* cheaper than actual locking diff
* cheaper than actual locking diff
* cheaper than actual locking diff
* ok, so no vacuum lines/servos to break after 15 years

EDL disadvantages:
* doesn't really "lock" the diff
* auto-disable can't be overridden for rally fun at higher speeds
* depends on ABS sensors/pump/brain not breaking

As you can clearly see, the advantages outweigh the disadvantages.

HTH
Henry
2 cars 2 old for EDL silliness