Seems to be a common issue on the automatic AWD trannys when a filter/fluid change is done on these. Fluid aerates and "rattles", this noise can be heard and felt in cooler lines to radiator. Some shifts may or may not be affected.
Many theories as to the cause:
1.) Aftermarket filters too restricted : disproven, same problem experienced when using OEM filters.
2.) Incorrect fluid used: disproven, same problem experienced when using OEM fluid or ATF III.
3.) Not enough room between pan and filter p/u: disproven too, people (myself included) have removed 1/4" from filter p/u and still have the problem.
4.) Leaking or misaligned seal on top of filter: again, disproven, no matter how perfectly you seal the filter, the fluid still aerates.
5.) Incorrect level of fluid: not the cause either, using the VAG tool to measure the level and temperature, the fluid level is perfect. Still has the problem, some have even tried more or less, no change.

I talked w/ our tranny shop guy and he suggests tightening up the valve body bolts and or replacing the gasket above it (if it has one -which I'm trying to find out).
An IATN post confirmed this could be the cause (leak in v/body gasket makes sense).
And lastly, the infamous breather blockage. There's a breather somewhere on top of the tranny (not the one on the final drive...BTDT).

So: Any pictures in KATE of breather on tranny?
and, any part numbers on valve body seal or gaskets?
Thanks everyone who's looking into this! It's much appreciated! -Many on the 100/A4/A6/A8 forums will thank you!!

1993 S4 Pearl on Black
RP370+ RS2 chipset w/ 3.0bar VMAP
AAN 4.0bar FPR
T4/T3 K26 hybrid Stage III hotside .63A/R 57trim
7A Exhaust Camshaft
Sport Exhaust Manifold
FMIC
Dahlback Racing bypass valve
Eibach S6+ Pro Kit Springs/Bilstein Sports w/ 20mm ECS strut spacers on rear shocks and 12mm spacers on front IGOR plates.
Nexen 255/40/ZR17 on Azev 17x8 ET40s
225/50/16 Nokian Hakkapeliitta IIs on graphite/polished lip refinished stock Fuchs in the shed for winter now.
European Lenses
4600K HID Low beams
4300K HID fogs
Auto dimming rear view mirror (gasp!)
Alpine HU; Infinity Kappa Components; Blau tweets
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1998 Audi A6(C4) Avant (Wife's)
Pearl on black w/ HIDs.
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1995 A6Q 12v 5spd (SOLD)
16x8 Wheels
245/50/Z16 tires
Ported and smoothed intake & upper/lower plenums, gasket matched intake to heads, ported TB and MAF.
S4 front clip
S6 interior and gauges
S4 suspension
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1994 S4 Green/Ecru testbed (Deceased)