I was wondering does a b5 a4 Quattro have a viscous clutch differential, or an open differential. If neither which one does it have stock. I'm having trouble deciding if I should upgrade and if I choose to what would be a hood direction to head

 

It's an open diff. The B5 didn't come with any sort of sport differential options.

 

So I'm pretty much sol, or are there any aftermarket options that you know of?

 

There are some for the S4 (which uses a different final drive) but I'm not specifically familiar with any options for the A4.

 

Pretty sure the wavetrac one will go into the front differential.

OP, if you are interested in a LSD rear diff, look into swapping in a 944 LSD. It has been done but requires some modding.

That's the thing that sucks about b5's. Some b4's got electronically locking center and rear diffs with the front always remaining open. Instead, b5's got stuck with open front, center, and rear diffs effectually making it an AWD one wheel wonder.

 

So with an open differential, does the b5 use an electronic differential lock? If so would a new differential disable that? Or is it a state that can be disabled by the driver, like traction control.

 

I believe it was only an option in 2001, but some a4's do have EDL. However, it has nothing to do with the differential. The ABS pulses the slipping wheel and the open diff takes over and transfers torque to the non-slipping wheel. Only in the back.