N62 Z3 Part 2: Transmission & Engine Fitment

Okay, time for part 2. There were some really big steps forward ...and a small step back. Lets pick up right where we left off - talking about transmissions and stuff

So it's sort of hard to describe, but the GS6 transmission has a "brace" on the back of it that can be bolted off - this, paired with different transmission crossmembers, allowed for fitment over a wide variety of applications. The current brace on the car extends back pretty far and uses transmission mount receptacles not suitable for an E36. But I could at least get an idea if it was in the right spot and see if things seem to fit when the transmission is in roughly the right spot. Good news is things seem to fit, the trans seems to line up properly and there is even adequete room for shift linkage!

But before doing too much more with that - I had to wait for the GS6-37 brace I ordered to see if it'd fit...

Next, a simple win - I replaced the two ABS lines I had removed when I relocated the ABS module. The second one I may re-do, but it will work for now. I realize these will never be "pretty" unless I re-bend them all from scratch, which I am not entirely opposed to doing. But I want to get it on the road first

Next, I wanted to focus on the areas that were causing fitment issues, I started by bending this brake line out of the way, as the engine was occasionally hitting the firewall and hitting the line. It's not pretty, but it is out of the way now. Also, it wasn't exactly pretty before so nothing was really lost...

I don't have any "after" pictures of the next step - but I trimmed a lot of random brackets out of the engine bay. Pretty much everything on the driver's side shock tower and frame rail except the clip for the round diagnostic port. Most of those brackets are visible in the below image... I'll take a good shot showing where they've been trimmed next time the engine is out

You may also note I trimmed the insulation on the firewall. I went a little crazy. None of that ended up needing to be done... anyways...

I was looking at the N62 and noticing that the A/C bracket looked very familiar. Sure enough - the A/C compressor from an M54 Z3 bolted right up to it. The rear bolt is in the right location, but needs a spacer and a longer bolt. This (probably) means I don't need custom A/C lines!

Next... my transmission brace showed up early! I got a text from DHL that my package was showing up from the UK and the only thing I had ordered from there is this brace. Went home for lunch and brought the brace off the transmission with me to check if the bolt holes lined up once the brace showed up. And show up it did but I swear when I compared the one I took off the trans to the one I bought, two sets of holes lined up and two didn't... figured maybe I would trim the holes to allow it to fit. Took it to the shop and ...well I'm just an idiot. It fit perfectly. And fit on the Z3 automatic trans crossmember perfectly

Getting excited now. I have applied a LOT of "If A =B and B = C then A = C" logic to this swap and so far it has yielded positive results. Now lets get the transmission in and see if it fits

I'm not gonna lie - there was very little drama with this process. It also did that really nice thing where the engine sort of just gravitated towards it's spot. As soon as I got under the car everything was pretty much lined up. I just bolted it in. I don't have the shift linkage yet though - and it seems very tight up top. There's a chance I may need to drop the transmission down a little bit to have adequate clearance for the linkage. Also - the first linkage I ordered was 100% wrong, I can tell without it even arriving yet. I ordered some linkage that should work for a GS6-37. Will that, too, work for the GS6-53 like the brace did? Time will tell...

I figure small spacers between the crossmember would work well to drop the trans a bit for clearance on top if needed. I will take a close look and determine if that needs to be done first - I really don't want to delay making the engine mounts until the linkage gets here and at this point it is ready to have mounts made!


Speaking of engine mounts - with the trans in place, the engine height will be determined by the driveline angle. Eyeballing it put me in the below location

It's definitely higher than where I had it sitting when I had it mocked up in place. Buuut... this location makes more sense and has better fitment literally everywhere. It may even be possible to do valve cover gaskets with the engine in place. Hooray for basic maintenance possibly not being an engine-out job

Oh and the hood seems like it will close... maybe just barely - the Valvetronic motor plugs are just barely touching the insulation - but it should work

Some other good news. I think. Not positive yet. But the steering linkage (the one farther from the camera) is attached to the splines on the firewall and seems like it will sit in the right spot. The picture makes it look a little closer to the header than it is

Note the header design - they merge in the middle, then hug the block as they go down before heading rearwards. Every single BMW with an N62 engine had a steering rack, so the headers were designed for steering rack clearance. The passenger side header I have already had in place, I just removed it to make it a little easier getting the engine in and out. The main question is the driver's side header but I am optimistic. I will also be cutting the catalytic converters off which will help a lot no doubt

So lots of good news... but, as promised, there is some bad. Potentially very bad. But there is always a solution

In the below image you will see an M54 alternator almost installed on the N62. It would fit, I'm not sure if that exact one would - something weird was going on with the nut on the back of that alternator, it was hitting the N62's alternator bracket. But I have another where the nut is recessed in the alternator housing properly and it fits. Anyways. Remember in part 1 when I talked about how they design the engine to be as wide as the heads? And the Z3 frame rails are not as wide as the heads on these engines? That's fine when it comes to engine mounts - just get custom ones made. It is way less totally fine when you realize the alternator is sitting right where the frame rail is

That may mean notching the frame rail. But it may not. I test fit the engine, then tried to fit the alternator in place. I couldn't get it angled around the bracket properly, the frame rail interfered. I'm going to try it again, but with the alternator being installed on the engine first, and installing the engine complete with alternator. If that doesn't work - I'm notching the frame rail Oh and the front subframe does need to be notched very slightly on the rear. It does technically "fit" right now - but the oil pan is rubbing the subframe. That's a bad idea. I'm going to take about 3/4" out the back of the front subframe. I will not use subframe spacers or anything else like that - the suspension and steering rack will use the stock mounting locations, in order to preserve the stock handling characteristics with absolutely zero compromise in that regard. In fact - I even believe the stock Z3 X-brace will still fit on the car! Which would be great, to protect the N62's plastic lower oil pan in a car as low as the Z3


So that's where I'm at now. I may end up in a position where I am waiting on the tune/EWS alignment/cluster stuff and have all the physical fitment stuff done. That wouldn't be the worst thing though. I have the DME with EWS as well as cluster out and ready to be shipped to their appropriate parties, as that stuff is out of my wheelhouse


Next time I work on the car, I will likely do the wiring changes needed and dig into the wiring diagrams a bit to try to find out where the last "unknown" harness goes and/or what it does


I did. I did do the wiring changes next time I worked on the car. Part 3 Here

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