UrS4boy

All C4 UrS sedans and avants came with power steering. In North America some of the C4 Audi 100s and A6s and all of the UrS4s and UrS6s came with the speed-sensitive variable assist "Servotronic" steering racks. These Servotronic racks used a Servotronic control module that, in turn, used signal from the G22 vehicle speed sensor to vary the amount of hydraulic assist that goes to the steering rack based on vehicle speed. At lower speeds (or stopped, as in parallel parking), the rack got more boost; at higher speeds, e.g. highway driving, the amount of boost was decreased. The option code for the Servotronic system was "1N3 - Speed-related variable steering assist (Servotronic)".

In the rest of the world (ROW), C4s, including UrS4s and UrS6s the Servotronic steering system was optional. The base power steering was coded "1N1 - Power Steering". While my Canadian-spec 93 UrS4 came with the 1N3 Servotronic system, my 94 German-spec UrS4 V8 avant just came witn the "1N1 - Power steering". Both work, just takes some getting used to the 1N3 Servotronic at low(er) speeds after driving the 1N1 non-Servotronic for awhile.

Okay with that background out of the way, there obviously is a difference in the steering racks that are involved.

Non-Servotronic Steering Racks

LHD

The 1992 non-Servotronic steering rack was PN 4A1422065 (later available as 4A1422065 X, where X is rebuilt). This was used in the 1991-92 Audi 100 (non-quattro V6), the 1991-92 Audi 100 Q and the non-Servotronic Audi V8 sedans.

The 1993 to 1997 non-Servotronic steering rack was PN 4A1422066 (later available as 4A1422066 X, where X is rebuilt). This included everything from the non-quattro C4 Audi 100s and A6s as well as the quattro V6, AAN UrS4s and UrS6s, the non-Servotronic Audi V8 sedans and, somewhat surprisingly, the S6 plus.



RHD

The RHD non-Servotronic C4 steering racks seemed to be either 4A2422066, 4A2422065X or 4A2422066X.

Servotronic Steering Racks

LHD

This gets a little more complicated for the LHD cars as there have been several different PNs used for the C4 Servotronic steering racks.

The earliest C4 Servotronic steering racks used in the 1992 Audi 100s and UrS4s were 4A1422065A (later available as 4A1422065AX where X = rebuilt). This rack was also used in the Servotronic-equipped Audi V8 sedans. Interestingly, if you dig deeper, the cores for the rebuilt 4A1422065AXs could be 4A1422065As (Duh) but also 441422065F and 441422065H from the C3 family. Hmm...

The C4 Servotronic steering rack for the 1993 model year (VINs PN000001 to PN150000) and part of the 1994 model year (VINs RN 000001 to RN038962 - end of November 1993) was 4A1422065AN. To confuse things a bit, there was also a 4A1422065FX (and presumably the 4A1422065F). Both the 065AN and 065F are listed for the LHD AAN and AAH (V6) engined C4s. Curiously, there is no specific listing Servotronic steering racks for 1994 C4s built in the Dec. 93 to June 94. Here are some PNs taken from a ROW parts diagram (NAmerica is subtley different)



Somewhere out there there was also an A41422065AF. However, it was dropped 31/12/1996 and replaced in the warehouse by the 4A1422065AN (which we know) and a pin, 4A0422129.

This one with a blue and silver PN tag appears to be an "AF"



This one, from Mushasho's UrS6 definitely shows as an "AF":


Photo Courtesy of Mushasho.

This one with a red and silver PN tag is an "AN"



And in the wonderful world of maintaining viable parts inventories, the 4A1422065AN was dropped from the inventory on 01/05/2004 in favour of the last C4 Servotronic steering rack, the 4A1422070 (and 070X).

The 4A1422065AN had been used in the 1995 MY run but only up to VIN SN075655. Then the 4A1422070 showed up. By the 1996 model year (perhaps including the 95.5 UrS6s in the US), the 065AN disappears from the listing, leaving only the 4A1422070 (now 070X)

1995 MY listings:



1996 MY listings:



Going back a subtle step, at some point in the 95 model year run (i.e. VIN SN075613), the passenger side steering mounting bolt changed from a M8 to a M10.



Again, if you dig deeper into the info, the 070X (the rebuilt version of the 4A1422070) can use both the 4A1422065AF and the 4A1422065AN as cores.

RHD

For the RHD Servotronic steering racks, the only PN that shows up consistently for the C4s is 4A2422065AK for all years.

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Special thanks to Yodasfro (Austin) for his early input on the Servotronic steering racks.

This post is not chiselled in stone and can be edited to reflect new info (or corrections), as needs be

moorewr

Servotronic trivia: you can unplug the servotronic unit and the power steering acts just like a non-Servotronic rack. This did not cause a CEL on my '95 (with 4A1 422 065AF).

UrS4boy

I am not a fan of disconnecting the Servotronic system but *IF* you must, I suggest removing the connector at the steering rack. In my experience, I didn't get any better steering "feel", i.e. preciseness, just heavy heavy steering.

My 94 S4 V8 avant has a non-Servotronic steering rack and it is much easier to steer with it than a disconnected Servotronic system in my 93 AAN S4 sedan.

moorewr

I agree with the above. When I realized the previous owner had unplugged (on the rack, next to the serial # plate) it I plugged it back in, and I've never touched it again.