I installed a manual transmission into my '86 735i in the summer of 2004. This is a challenging project, but well worth the time and effort required. I cannot emphasize how important it is to have a complete set of the parts you need in order to do this project. Once you start working, it's hard to stop. The only reason I would stop working was if I didn't have the next part. It is entirely possible to do everything in one weekend, especially if you have a partner. I would say the two most challenging parts were the installation of the pedal box, and trying to figure out the modifications that needed to be made to the wiring system.
While working on the wiring, I took some pictures that should help to explain what I did with the wiring. I had read a few different pages on the internet, but none of them really explained what needed to be done, especially with some pictures, and they also wanted me to make numerous splices into random wires under the dash. I wasn't comfortable with doing it this way, simply because I assumed BMW had designed the wiring so that either a manual or automatic setup could be easily installed in every car. Basically, there are three different systems that need to be wired when performing a swap.
1. Bypassing the neutral safety switch
2. Connecting cruise control to the clutch pedal
3. Hooking up the reverse lights
1. Neutral Safety Switch
The NSS is built into the automatic shifter, and sends signals to a starter relay. The purpose of this design is so that you can only start the car in Park or Neutral. Bypassing the circuit is easy. Remove the kick panel above the driver's feet. There is a glob of wires and connectors that hangs on the lower end of the steering column. Push in the tabs to and slide the connectors out, off of the steering column. Here's what you'll be looking at:
Dig around under the dash some more, until you find the connector in the foreground of the above picture. It has a Black and White connector, with Yellow/Black wires and one large black wire coming from it. Remove the black plug with the single black wire coming from it (on the steering column wire connectors). Unplug the black connector with the Yellow/Black wires, and plug it into the connector from the steering column. You have now bypassed the NSS. For neatness, plug the two loose connectors into each other. When you're done, it should look like this:
Now clip the connectors back onto the steering column, You do not need anything plugged into the connector from the automatic shifter, just leave it flopping around the console, unless you want to take the time to remove the wire set from the car...that's something I didn't car too much about.
While you are under that area of the dash, take off the left speaker panel and remove the transmission computer. Sell it on ebay.
2. Cruise Control
Once again, BMW made this easy. Dig around under the dash and find a connector with a loop of wire connected to it. The wire is Yellow/Red.
Pull of the loop of wire, and plug in the clutch pedal switch.
Now mount the switch to the pedal.
Simple.
3. Reverse Lights
Your manual transmission will come with a reverse light switch. It will be mounted on the side of the transmission, near the top. Cut some wire, and add female connectors to the end that will plug onto the reverse light switch. Run the wires through the clips on the side of the transmission, and up through the hole that the shifter comes through. It doesn't matter which wire goes where. Next, find the connector shown below, it will be near the hole for the shifter on the center console.
From the left is the power supply and the connection to the reverse lights. Typically, you would unplug the right side connector, and install the wire that BMW would have supplied. A connector that takes the place of the one on the right, and plugs into the reverse light switch. The switch simple completes the circuit when in reverse.
Instead, I left the automatic setup in place, and on the right side spliced in the wires from the switch, one for each pin of the connector. To splice into the wires, buy some of those neat splice connectors that cut the insulation, make the splice, and have a little door that covers the metal (Look at the first and second pictures on this page for the red and blue connectors. That will keep things looking organized). The added benefit here is that the "R" on the instrument panel will light up when the car is in reverse.
Hope everything works out well. Below is a link to some wiring diagrams that will further explain the circuits if you are more curious:
If you have any more questions, feel free to email me.
7/8/04
Kevin Elmore