Huston, we have separation!

After a week or so of fighting under the car and tearing out every little connection I could find, the engine and transmission are finally free and have been removed from the car.

The process was grueling. There were so many tight areas that I had to get my hands and tools into, and what made the whole experience that much worse was the horrific build up of oil and grease that encased every inch of the drivetrain.

I started out by pulling the radiator off, along with all of the air conditioning components attached to it. There was also some power steering components there, which had the special BMW push-pop connector that I could not get done for the life of me, and I just cut the loop. I’m not using power steering anyway, it was busted when the car arrived and it handled fine.

I then worked on the electronics. I unplugged a ton of connections, like the mass air flow, VANOS, thermostat, etc… Next came the whole harness connected to the engine computer by the steering column. That came out real easy and it was nice that it was just one large connector.

I realized at this point, as noted in my previous article, that the all wheel drive system was integrated into the oil pan. The differential for the front wheels was attached and ran directly through the pan. This meant the axles going to the front wheels, along with the drive shaft coming up from the transfer case, were firmly holding the engine in place. And likely they were the only things holding the engine in place, because the engine mounts basically disintegrated when I went to loosen them.

So I removed the front wheels and hubs, popped out the front axles, and began to shift my work under the car.

Then came the exhaust. This one took a while, since exhaust bolts are always so corroded that there is no real easy way to loosen them. After a day of beating on them, I was able to shape two of the nuts into cylinders just small enough to slide through the bolt holes. The other two bolts had to be cut with a die grinder. It was tough but it worked, and it came right down once they were gone.

I then removed the rear drive shaft from the transmission in order to free it and also allow me to reach above to disconnect the shift linkage. After that, there were some other shields that came out and the clutch slave cylinder. There was a support brace that held the transfer case up, so I loosened it quite a bit to see how loose the engine was. It seemed like it was almost ready to go.

There were still a few things that needed to be done, and I wasn’t entirely sure on how to do some of them. I knew I had to attach the engine crane somewhere, but there was only one lift point that I could find. I tried taking off the manifold to potentially access another point around back, as I have seen in some videos. But I dropped my torx bit into the engine and figured it probably was not worth the hassle.

After getting some other things taken out and freed up, I chose to drape the chain down behind the engine and attach it around the drivers side engine mount. It seemed to make a stable point to pull from, and it was definitely strong since it’s held this engine this whole time. It was a pain to reach and also awful trying to secure the chain with bolts and washers, but I eventually got it.

So I just began pulling up with the crane. I knew things were not perfectly undone just yet, but I’d do them as I found them.

As it turned out, I was quite right with that assumption. The first issue I ran into was the oil pan and differential were getting caught on the steering rack. I tried to pull the engine from a different spot on the chain to get it to aim upwards differently to potentially clear it, but that didn’t work. Eventually, I had to use a breaker bar and remove the two front subframe bolts to let the steering rack drop about 6 inches, at which point the engine came up quite high finally.

But as I kept going up, I noticed it started to bring the whole body of the car up with it. I assumed the transmission was getting caught, so I kept trying to jack it up from under the car to change the rotation of the engine. I wasn’t totally incorrect, as it did get stuck up against the top of the engine well and lifted a bit, but the main issue was the AC compressor. I forgot to take off the line going into the cabin.

Once that was sorted, it was moving a lot more. It still was having clearance issues though. Mainly the transmission was being pivoted so much that the drive shaft end was on the ground while the engine was a good 3 feet in the air. That meant the transmission wouldn’t clear the sub frame and kept getting caught there. Eventually, with a combination of the floor jack under the transmission and constant adjusting of the engine hoist, it became free.

There were still a few electrical connections, like the catalytic converter wires and some vacuum lines, but those were pulled easily. Finally, it was out.

And my, was this a beast. It was probably about 8 feet long, that transfer case definitely added a bit of extra length.

I then spent the next day trying to separate the transmission from the engine. That was a whole other ordeal for very different reasons.

The transmission had a stripped bolt on the bottom, so again I had to grind it and cut the head off so I could just slide the transmission out over it. I also had to take the front drive shaft out, which was a little bit of a pain since it kept wanting to rotate. Thankfully with a screwdriver shim and a quick twist instead of a constant pull, they all broke free and the shaft came loose. With a bit of prying and kicking of the transmission to get it to separate, it eventually came free. It’s so much smaller when it’s separate and much easier to work with.

But alas, another issue has arisen. When I spin the transmission input shaft, where the clutch usually meets, the shaft for the front wheels spins instead of the drive shaft for the rear wheels. It appears BMW designed the transfer case to rely off of the resistance from the front wheels to decide how much power goes to the rear ones. It makes sense but that is the exact opposite of what I need. I believe if I make a plate and affix the front output shaft in place so it can’t rotate, all the power should go to the rear wheels. I just don’t know how strong it needs to be, like how much force does it take to divert all the power to the rear wheels? I guess I’ll have to experiment and find out.

Next steps. Making an adapter plate for the electric motor. Make a adapter coupler for the electric motor and transmission using the old clutch. Find a way to stop the front drive shaft from turning. Get controller. And that’s really it. I am excited for the next week or so.

About the author

Jameson Toper

I am a Computer Science Student at the Rochester Institute of Technology, and I have a strong passion towards the field of electric vehicles. When I am not working on this project, I teach a Computer Science course and make music.

View all posts


  • Hi Jameson,
    Unfortunately the torque split and the planetary gears in the transfer box dont work the way you think they do. As soon as you spin the box under load with the front output pinned stationary, things will get very hot or break. Something needs to be modified inside the box to make it RWD only.
    If you have the time and someone who is an experienced fabricator available it would be better to make a frame to carry the front diff and outrigger bearing and keep the AWD. If you want this to actually work there is a lot of stuff that needs to be designed and built to hold all the component parts in the engine bay besides the gearbox adapter, and motor mounts.
    If you would like to chat about some of the possible options perhaps send me an email. cheers

  • Hi Jameson,

    great idea of yours and I have been playing with the same idea, in my case an E46 320d with automatic transmission.
    Will the EV conversion work with the autobox or should one need a manual?

Leave a Reply

Your email address will not be published. Required fields are marked *