There are two choices for the remote piece itself:

Choice 1: 2 button transmitter is $ 50.57 (Clair) Part# 4d0837231d01c
Choice 2: 3 button transmitter is $ 46.71(Clair) Part#:4d0837231e01c

There is an optional snap in component for both Choice 1 and 2, however you do not need it for the remotes to function:

Folding key is $ 68.00 Part#: 4b0837246a

The key has to be cut at the Audi shipping depot; it cannot be cut by the dealer. The final programing will have to be done by a dealer. To order keys (not remotes) you must have a copy of your registration or VIN # to verify proof of ownership.

Ok, this is how it works to get a Remote Keyless Entry system on your *1998* A4. (These instructions have not be tested for previous or future year model A4's).

First, you have to decide if you want the 2 or 3 button remote. The two button remote has a 'lock', 'unlock' and 'panic' button. I dont know what the 3 button has, but I believe it is the A6 remote.

The 2 button remote is part of the folding key remotes. You can use this portion of the keyless entry system without buying the $68 key. It snaps in to the folding key portion, so if you dont get it, it doesn't look 'perfect' as it appears like something is 'missing' when its not.

After obtaining the remote, call your dealer and schedule a walk-in appointment as it only takes 15 minutes to do. You must give the dealer your remotes and two keys. They will get into the A4's computer and do a reprogramming to in effect 'activate' the receiver to accept the remotes PLUS code the receiver to the remotes special access code, which the dealer figures out for you. This will cost you in the $50 range depending on how long it takes them to figure out.

Note: Applies to US models only.