GS6-37BZ Six Speed Swap Guide for E34 525's

[peakcomp]

@singing6: Great write-up, this has inspired me to undertake this project on my 92 525iA touring.

Not sure if I missed it but do you have the exact length of the modified driveshaft you are using? I am going to see if I can find one that fits out of the box'ish'. Also, what is the 3.46 LSD out of that you are using?

My setup will be as follows
- M50NV with 140k
- ZF GS6-37bz from 04 ZHP
- Large case LSD from 91 M5

Thanks in advance - Dan

[Onizukachan]

You should go back and read Morozas posts, or even the thread again. He already figured out a drop in for you, assuming your diff has the right flange size.

[moroza]

He already figured out a drop in for you

*On paper*

I'll confirm whether it works in practice very soon.

UPDATE: confirmed. 530iA <10/93 driveshaft fits M50 E34 with 37BZ and medium-case diff with 86mm input flange, if used with M3 giubo. The CV is pulled by 3mm, which it seems to not have a problem with.

Using a large-case diff shortens the driveshaft length required. OP and I are using medium-case diffs.

[8erBN]

Hi, jumping on the thread. I am from asia and I own an E36 auto m50b25 single vanos (eur), i think it has a 3.73 rear differential.

How different would it be if i swap in a Manual GS6-37bz box? What parts would i need to achieve this

Hoping to get some lights shed

[moroza]

Hi, this is the E34 forum. Fitment to your engine is the same, including everything about the clutch and flywheel, but otherwise none of the information here will apply to your car.

[5spd525ikid]

@moroza and @singing6

thank you for the detailed information. This is extremely helpful and you did a ton of work putting these measurements together.

can you elaborate on where to take the measurements from on the CV in order to come up with the 86mm? Unfortunately I don’t have a driveshaft to refer to. Also, I am assuming it is the e36 M3 quibo that needs to be used?

is the 530iA driveshaft built from/after 10/93 completely out of the question to use? Seems like only 4mm in length wouldn’t be a deal breaker but maybe I need to understand firsthand the 6mm difference in the CV between the two.

thanks!

[moroza]

86mm is the diameter of the circle formed by the six studs on the CV joint at the diff input.

E36 M3 giubo is the same part as E46, and is the one I used.

E34 530iA shaft came in two flavors: up to 10/93 were 1511mm and 86mm CV, and later ones 1521mm and 80mm CV (a different PN from the 525iA piece). The two 530iA CV have different tooth counts and are not interchangeable. Everything else is the same, and AFAIK the diff input flanges are shared with 525i of same size.

One conclusion is that no matter how I count, either of the two 530iA shafts is within 10mm of the derived solution, if used with its native CV: 1480mm for the early 86mm, 1490mm for the later 80mm.

Since posting that, I've personally verified one of the derived solutions, so I can say with some confidence that the other will work as well.

[5spd525ikid]

86mm is the diameter of the circle formed by the six studs on the CV joint at the diff input.

@moroza

i think I comprehend now. For instance, if I were to be doing just a typical 5speed swap is an auto 80mm CV 525i (per your measurements of 525iA vs 525iM cv) then I can only use the driveshaft that correlates to the diff flange size. Therefore, I could not retain a 4.10 ratio 525iA diff in the car if it’s 80mm Flange and would need to swap in let’s say a 3.73 ratio 86mm diff flange (which is what most people do anyways since the RPMs would be grossly high with 4.10) to match the 5speed manual 86mm CV driveshaft when using the 310/320 ZF gearbox.

Sorry, I know this is straying from the 6 speed swap but I think it’s just helping understand why there is such importance to match 80mm CV driveshaft to 80mm Diff and 86mm CV driveshaft to 86mm Diff flange.

Regards,

Ray H

[moroza]

Diff flanges are easy to swap. 4.10 is indeed too high for a 37BZ (I use a 3.07. The result got 28-30mpg highway at 70mph, in a Touring with its worse aero).
Picture 3009.jpg

[Singing6]

On that note, I feel this is a good a time as ever to give some updates on my build after over a year of fiddling.

The trans:
Perfect. So much better feel than any of the stock transmission for these cars. And the more time I spend around the ZF’s and Getrag’s, the more I start to hate all the Getrags. Their internal shifter mechanisms in particular always feel more sloppy.

The shifter:
There were a few iterations here, and more are still to come, but a few lessons learned.
1) Don’t bother welding the material the shifter support arm is made of. It is such a low quality aluminum casting that, combined with the oil it is going to have been soaking in for the past 15-20 years, it is not going to weld nice. Lots of porosity.

2) Stay the hell away from anything Garagistic makes. Their DSSR’s in particular. It had slop from day 1 and they always will as long as they use their current construction methods. You cant hold good tolerance on a bent metal flange that you then weld next to. Not to mention their crappy pins.

3) I now hate the oval shifter support arm bushings. When I get off my butt and finish the work for this new shifter setup, it will get rid of all these problems, but at a great cost. A fully custom, billet aluminum shifter support arm designed and fabricated by me. The cup mount was by far the hardest part I have ever made and I’m NOT making another. (Pic below)

The new system also includes a UUC DSSR that I modified to have the correct bend and length. Im still using the Schmeidman adjustable shifter rod and still like it. There is a noticeable increase in NVH from it, but for the better feedback, I love it. The needle bearing at the bottom is overkill though. I would prefer the UUC design with a proper sealed bearing.

Driveshaft:
As some of you reading this know, I turned the first shaft into a Twizzler. It was a combination of cheap metal from the shop that made it for me, wheel hop from trashed RSTM’s, user error (not backing off when the wheel hop started), and my measurement error, causing the shaft to be 12mm too long.

So I fixed all those issues and had the shaft remade by the same shop. They covered more than half the cost and made it out of drawn tube this time. Well, apparently they don’t know how to weld and so I broke that one as well. And at unofficial Vintage 2020 no less:


They covered the full cost of repairs this time, but I no longer trust their work on this project and so I got my hands on a pre-10/93 530iA shaft (two actually), and will be swapping that in soon, likely along with the new shifter. But for now, no clutch dumps.

Speaking of clutches, the flywheel clutch setup:
The stock 330 setup works. But it has chatter out of the box with brand new Luk parts and after asking around, that was normal from the factory on the cars this trans was supposed to be in! It is heavy and a stupid light pedal. I switched from the G250 20mm bore slave to the e36 328 22mm slave to try and stiffen it up a bit. It helped, but not enough. The shifts just did not feel right. The flywheel is actually heavier than the stock m50 stuff. And I hated the self adjusting pressure plate from the moment I saw it. I played around with some really odd options including a UUC s54 LWFW with a JB Racing pilot bearing adapter and euro 2011 n47 manual x-drive clutch, which is sprung hub for some reason. None of these options fit. I finally did find a solution though; the JB racing LWFW (520-190-240) and Spec (SB-071s) stage 1 organic clutch.
(Dont forget that “s”, it is how you make sure you get a sprung hub!). This setup gave a 45% drop in rotating mass (which is the weight of the pressure plate and flywheel) and is AMAZING. The shifts just feel like they line up. And the pedal is nice and stiff. Despite the much stiffer pressure plate than the 37bz normally has, the big e34 hydro clutch mech makes it feel very close to what a stock e34 feels like. But with a lower bite point. There is lots of chatter, but it is well worth it, and the engine sounds like an NA diesel below almost exactly 2000rpm (clutch in or out). Im pretty sure it is the sound of the sprung hub doing its job, but I got to inspect it at 1100 miles (thanks to that second driveshaft failure) and it looks perfect. Also note, NEVER get the brass pivot pins. They wear out super fast. It was ⅓ gone after 5,000 miles and ½ gone after 15,000.
I replaced it with the genuine BMW stainless pin used on the V8 and V12 manuals. But right after I got this, Angry Ass Solutions started selling a greasable SS pivot pin. So next time its apart, that goes in.

Mounting:
The Rouge engineering trans mounts have held up great and I still love them. I recently switched from stock, new corteco, m50 motor mounts to Bimmerworld e46 m3 “group n” mounts. You have to shave off the locating dowels and then “clock” them in the orientation that makes everything line up, but then they are fantastic. I love the way they feel, and can notice the extra control in the corners.
There is again a noticeable increase in NVH, but it is mostly at idle. The engine also got a 900 rpm idle thanks to the flywheel so that likely has smoothed some of it out.

Diff:
The 3.46 can suck it. It had to come out anyway due to a failing bearing, but I was happy to put the 3.23 back in. Plans are to go turbo with this car in the near future and so I will likely be swapping to a ratio in the high 2.xx range, but the 3.23 is amazing for now. I understand why @Mozora is running his 3.07. The 3.46 just makes the whole swap feel like a waste of time for so little bump in “go”.

Man, it feels good to post this update. Hope this info helps even more people. Im sure going to continue to develop it!

Singing6

[Singing6]

Oh, and one last note on exhaust hardware. I did not know it even was a thing at the time, as mine had completely rusted away, but there is SUPPOSED to be a mount from the transmission to the exhaust next to it. If you drill a new hole in the bracket, it all bolts up with the e34 525iM parts and the e46 330 trans bracket.

Right now the fitment is not quite perfect, it is a little twisted, but that may be due to my other exhaust modifications. The point is that it is close enough with very little work.

[moroza]

You're alive!

Good stuff, especially the pressure plate info.

I recently took my shifter setup apart, bought a 2" 95-durometer hard rubber tube from McMaster (~$10 shipped), cut and shaved it down to be a very firm but not completely rigid set of oval shifter carrier bushings. Oh, and you wanted to see this..





I used that exhaust brace at first, as it came with my trans, and I found it greatly increased exhaust noise. Sounded properly good, but droney. I didn't have to drill any holes to fit it.

[Singing6]

I gotta say, that looks horrifying. What are the two screws going into the bottom of the shifter rod?! Why are they DIFFERENT SCREWS?! Why did you not get proper shaft stock that is ground to spec?

On the exhaust, I did not notice any real difference in NVH, but I have a lot more than you anyway, so it may simply fall under the radar. Though, were you using the factory rubber isolators? I am.
Here is a photo of the new DSSR to go in. Used a partial pie cut method that let me bend this without destroying my 20 ton finger-break tooling.


And here is another pic of the sweet sweet JBR flywheel.

[moroza]

Yes, my exhaust brace came with OE E46 rubber.

IIRC, I threw that together to test as a quick-n-dirty proof of concept, intending to use a different lever for the final piece, and preferred this lever after all. Different screws because it's what I had on hand and it doesn't matter (they aren't even necessary). If by "shaft stock" you mean the bronze sleeves, it has two $1.42 US-made 10x13x10 bronze sleeves instead of one because I couldn't find a 10x13x20 in stock anywhere and wasn't about to pay 2-3 figures for a custom-milled one. If you mean the part that goes inside the bronze, using spring pins was precisely the point - they spring out against the bronze, acting as tensioners to take up all slop.

The form isn't the prettiest, but you can't see it anyway; the function is excellent, longevity seems promising, and that's what counts. Where form counts, I have this just a few cm above:


Give me your kind of budget and I can make things as shiny and pretty as any. My budget means reserving pretties for where it matters.

[Singing6]

It still looks like a war crime down there


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[moroza]

Feel free to take forever and a $20k Tormach to make a nicer-looking version. It works, it feels great, and it's holding up fine. My resources and I have moved on to other tasks.

[Singing6]

A $50 Used UUC dssr was not that expensive and only took a few hours to modify. I’m not a bag of money, and I take a long time to get it all right. I also do try to find the best deals on parts!


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[xcastaway]

Having had the opportunity to test out the feel of Moroza's shifter, I can attest that it feels snug and smooth, and shifts quite nicely. Aesthetics in inaccessible locations, while they may soothe one's OCD, are definitely of lessor importance to function.

[Dionk]

I drove the authors car today. Shifts are clean and crisp. I will be replicating this 6 speed / diff swap bolt for bolt. Can’t wait - my e34 touring life is currently “auto-tragic”. Would recommend.

[AlphonseHavoc]

Feels good to drive I have received the honor of being allowed to move drive and wash it while the owner is away from time to time.

[Sleepyhead97]

It still looks like a war crime down there


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. You guys are killing me. I say do what works. Function over form all day long. I am deeply grateful for this info

[Singing6]

Just created a google sheet (Microsoft excel, but online) for the swap with every part that that I used. Has a tab for both auto to manual and manual to manual. Will also be adding it to the top, but here it is:

https://docs.google.com/spreadsheets...AJhvi09yA/edit

Feel free to ask questions.

[Singing6]

. You guys are killing me. I say do what works. Function over form all day long. I am deeply grateful for this info

It is just a matter of pride in my work. Don’t get me wrong, function always comes first for me (its why my paint still looks like shit and there is still a 5-speed logo on the shifter knob), but I also want the mechanical solution to be clean and simple. I mentor for the local high school robotics team and see enough hack-jobs and jerry-rigged solutions there! I am sure that Mozora’s stuff works great.


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[Sleepyhead97]

It is just a matter of pride in my work. Don’t get me wrong, function always comes first for me (its why my paint still looks like shit and there is still a 5-speed logo on the shifter knob), but I also want the mechanical solution to be clean and simple. I mentor for the local high school robotics team and see enough hack-jobs and jerry-rigged solutions there! I am sure that Mozora’s stuff works great.


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You did great work. I just see myself doing whatever works. Some people are just really great at making custom work look like a million bucks (you) . great work. Im sure having robotics exp helps tremendously

[Singing6]

You did great work. I just see myself doing whatever works. Some people are just really great at making custom work look like a million bucks (you) . great work. Im sure having robotics exp helps tremendously

Thanks, that means a lot. I would say it is more of fabrication experience, but hey, whatever works.


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