Welcome
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My Jetta has been converted to 4Motion and this site is intended to help anyone who might be pursuing a similar project by providing technical info, parts info and lists, and other finer details that we mostly discovered on our own.

Most of the work was performed at Bluewater Performance in Denver, Colorado. Additional help was provided by Double J Motorwerks in Portland, Oregon.

The donor backend was purchased with the help of Cascade German in Portland, Oregon and Korwerks LLC in Westtown, New York.

The upgrades:

Click here to see a gallery of the project.

Wiring
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One thing we learned after the fact is that many of Korwerk’s customers installed manual switches to activate 4Motion rather than rely on the native features of the ECU. This is speculation, but this may have been do to a lack of info regarding wiring changes need for cars with ASR/ESP. Rather than re-write everything here, I will link to a post I made on the TDIClub Forums. Basically, you will need install jumper pins in the connector for your ABS module. As simple as this sounds, it took months of troubleshooting to find the eventual solution: https://forums.tdiclub.com/index.php?threads/4motion-retrofit-and-abs-module.523232

Parts
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Most of the parts you will need will come attached to the MK4 backend you purchase. However, be prepared to replace many bits and baubles because these cars usually come with a lot of rust. Below will be a link to a Google Sheets doc that is a comprehensive list of every part you might need. However, you should also try to acquire some specific additional parts from the company from whom you are purchasing the sawed off backend. These are parts that have been canceled/No Longer Available/NLA by VW for many years. You will find most of these are the 4Motion-specific versions of these parts. Basically, anything 4Motion/R32-specific, whether interior or exterior, will be nearly impossible to find.

  • ABS Module: 1C0907375P or 1C0907379P, you might see it sold with either number, but it’s the same part whether it’s a US R32 or a Euro 4Motion Bora/Golf. Since this is in the engine bay, it won’t usually come with your backend.
  • Rear ABS Sensors: 1J0927807D x 2, 4Motion-specific. These may come on your backend, but they’re probably trashed, so prepare to buy new ones.
  • G251 Module on Steering Column: 1J1907638F, this is the 3-sensor version of this module which has yaw, longitudinal speed and latitudinal speed sensors. This sensor is almost impossible to find in the US. However, it is the same sensor used on the R32, so you maybe be able to locate one from a GLI/R32 salvage site like One Love Auto.
  • Carpeted Trunk Trim: Since a 4Motion trunk floor sits 5 inches higher, the carpeted trim parts are 5 inches shorter. Since many of these backends are stored outside, they may not come with these parts, or they may be trashed. The hatchback/wagon parts can sometimes be located on eBay, but the sedan parts are super rare because not many sedans were made with 4Motion. I highly recommend trying to get these parts from your backend reseller at the time of purchase. Otherwise, you may never locate them. And, due to their odd shapes since they are carpet on top of molded plastic, it will not be easy to re-create them either.
  • Lift Pump: The official part number 1J0919050A is impossible to find, so if your donor car comes with a bad pump, you might have an issue. The pump differs from the front wheel drive pump because it has an extra nozzle that connects to a secondary part in the other half of the tank. A 4Motion tank is split in half by the propeller shaft, so the OEM lift pump has two halves. If your pump is bad, one option might be to disassemble it and try and find a part number on the pump mechanism itself. You may be able to find one. However, don’t just guess because I believe there are multiple pump mechanisms with different PSI depending on the version of the car.

This is a Google Sheets file I created to keep track of all of the parts I had to order. These were items that were usually too trashed to use from the donor backend, or they were parts that didn’t come with the backend: https://docs.google.com/spreadsheets/d/1ZtztQrpMVnbKWNCD3N6OXlLiFr8Hi6HwfWnhi9Q7Itk