N62 Z3 Part 17: Finalizing Fitment (Transmission)

Back to work on the important things of the swap, the next critical step is aligning the driveshaft and get a custom driveshaft made. The first step for that is to establish the gearbox height. It is too tight of a fit in the trans tunnel and needs to be lowered a bit

I have been thinking of two solutions to this problem:

First is a trans bracket spacer - something to sit between the trans mount bracket and the chassis, in order to lower the trans by the height of the spacer

Second solution was a custom trans bracket that dropped where the mounts were relative to the chassis bolt holes

I went exploring and found both of those things in the factory parts catalogue

Transmission spacers are these part numbers: 41122256493 & 41122256494 - I believe they need to be welded to the body and they seem to also act as a reinforcement. E36 M3 Group N and Euro 3.2 (w/ 6 speed) cars got these spacers installed from the factory

I also found the E36 M3 3.2 Evo trans bracket looks like it is a little lower at the mount location... I ordered the trans mount, but didn't order the spacers, as I wasn't sure that was going to be the right size for my application and they are pretty simple to fabricate myself

(Note: once I had these parts in hand, I realized the Euro trans bracket is not compatible with this transmission as the bolt holes are too far apart)

Don't mind the dirt but with the Euro trans mount in, I could compare it side by side to this stock E36/Z3 trans mount I have on hand and it does indeed mount the transmission lower relative to the chassis

However, the stock trans mount was designed to account for quite a few different transmissions and as a result, has different mounting holes drilled in it. I've been using the furthest forward holes, which allows me to mount the trans as rearwards as possible. However, the E36 euro trans mount was only designed for one car - and only has one set of holes as a result. Holes which are in the wrong location. Dang

The perspective in the below image makes it a little hard to tell, but the round holes on the Euro trans mount (top) are in the location of the oval holes on the stock E36/Z3 trans mount. I've been using the round holes so the transmission is not in the correct place using this mount as it moves the transmission too far forward.

So the next move will be to get a spacer manufactured. There are two ways to do that that I can see - depending on which trans mount I want to use. I can make really tall spacer, to lower the stock trans mount to where I need it. Or I can make a smaller height spacer with new holes/threads drilled offset rearwards from the original and use that with the Euro trans mount

I also ordered a shift carrier and it didn't fit either, although I wasn't really expecting it to. I was originally planning on ordering the 545i shift carrier which was longer than this one. Makes me wonder if the 545i one would have worked... I may order it and see. These aren't too expensive

This is a measurement device I created and had a friend 3D print to help align the driveshaft

The idea is pretty simple - it will bolt to the transmission output flange (or giubo) with a Bosch laser distance measurement device designed to fit right in the middle. The laser outputs centered from the giubo. The idea is to simply bolt it to the trans and then move the engine/transmission until the laser points to the center of the rear driveshaft r0which is still installed in the car. The Bosch laser device I am using is also a measuring device, so it will also tell me the length the front driveshaft needs to be

Giubo with the laser measurement tool installed

The laser measurement accounts for the length of the unit too, which is really convenient

The unit itself installed in place

Showing where the driveshaft "aligns" to - a little high right now

In use - the laser isn't perfectly centered in this video, but you can determine center by finding the center of the circle

Oh and Go Suns! Game 2 against the Nuggets was last night!

So much hype!!!

Anyways... working on the transmission mount spacer. I printed templates in 1:1 scale and used them to mark the pieces I will be using. I am not sure I would use this method again for something so simple but I liked the idea so I just went with it

Then got to drilling pilot holes. I would have used a step bit, but it wasn't my equipment and the person I was working with preferred a hole saw for the big holes and drill bits for the smaller holes. It worked well enough so no complaints from me

Got the holes all lined up, whew!

First big hole drilled...

All of them drilled

Then I welded up em together to form the spacer, each side of which consists of two plates

Then the smaller holes were tapped for the original transmission bolt threads and below are the finished products. I will paint them next time the engine is out but wanted to make sure they did not need further modification before painting

Next up was to shave down the heads of some bolts to the right height, they need to sit flush with the top of the spacer

Mocking up how the crossmember will bolt to the spacer to make sure it all fits - looks good!

Spacers installed in place

And finally, the transmission crossmember installed. It's designed to use the rearmost bolt holes and since I am using the stock mount currently this could also mean I could go a little further rearward if I wanted to

Also, even though it uses the rearmost bolt holes I built the spacer to move the engine rearwards an extra 10mm over where the front most bolt holes placed the engine before. So, even though it is using the rearmost bolt hole location it is actually 10mm further rearward than it was previously

I have clearance up top for shift linkage now!

Laser alignment looking good... wasn't totally dead-on when I spun it around though

Next up is to roughly set the engine height and then finalize the transmission height before making engine mounts

To be honest though the engine looks to be in a pretty good location as it is! Tucked as far back as it can go. There is definitely more clearance to the firewall but there isn't any more room in the transmission tunnel. Even just moving it back this amount will likely necessitate a little more clearancing around the trans tunnel

To finalize the engine height I removed the radiator support and the alternator to have better access when the time comes

And also took a moment to see if I had space now for the shift linkage... looks like I do!

In some of the above images you can see the transmission mounts are under tension - this is because the transmission was hitting at a few places around the front of the trans tunnel, preventing it from sitting in it's correct position. So I decided to mark those areas and then remove the engine to clearance them a bit. Not particularly scientific, I just gave the areas some precision whacks with a sledgehammer