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Old 07-26-2014, 09:13 AM   #1
drift.mechanic
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HOW TO: E39 M5 trans into E46 non M, must have info for all inside

I'm not super active on the forums, but when I am, I'm sharing info. I'm blessed with over 10 years in the repair and build racing world and don't plan on stopping anytime soon.

I drive my 323IS daily, and travel roughly 50k each year. Every time something needs replacing, a full race version takes it's place. My most recent upgrade was a 3.46 final. It really woke the car up, but 3,500 @ 120 is a downer.
What to do? 6 speed. Options? M3 Getrag 420G, strong, hard to find and very expensive. ZF 330 6 speed, weaker than the Getrag, still hard to find and expensive for what it is. And now, there's a 3rd option that has since now, only been a rumour.

The E39 M5 or 540I V8 6 speed, also a 420G BUT uses a V8 bellhousing almost twice the size of the I6 counterpart. I scoured the net in search of the answer, and contacted Getrag (no reply), and haven't found an answer to the 15 year old question "Can the bellhousings be interchanged?"

Answer is... YES.

After an unfortunate incident to an acquaintance's E39 540I w/ M5 swap, I ended up with his low mileage 6 speed.
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Covered in oil from the rollover, she needed a cleaning... And a new bellhousing. Before doing anything else, I opened her up and inspected everything, and happy to report, gears are in near new condition, shift arms are straight and without wear, synchros are in brand new condition. Basically, brand new condition internally.

Since it checked out, time to find a 6 speed bellhousing.
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M3 on the left, M5 on the right. Visually, they're very very different on the engine side, the V8 being almost twice the size. Although the gearbox mating surface looks the same, I haven't proven it yet (in that pic, but I will later, keep reading).

Time to compare internals:

- M3 bellhousing (SMG housing, misinformed member advertised it as a manual... GRRRR! Thank god the price was worth it.
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- M5 bellhousing
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Obviously the M3 bellhousing is lacking the shift return spring assembly. Not a problem since the V8 bellhousing has all the components in immaculate condition.

Now the reason you're reading and how I proved it.

Can you take the 420G from a E39 M5 and swap bellhousings with a E46 M3 to obtain a hybrid 6 speed? (I'll explain after why this is beneficial).

Yes you can. Here's how you prove it:
I've built transmission adapters for Nissan I6's before; RB25DET to 370Z 6 speed, 1JZ to 350Z 6 speed, B18C to Nascar 4 speed...
What's the best way to do it? Get your arts and crafts on!
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A simple sheet of printer paper and a pencil. Lay the paper over the mating surface as flat as you can in a way to reach as many bolt holes as possible. Once laid, hold it in place with one hand and run your index of your other hand along the machined surface to create pleats in the page. Follow those pleats with a lead pencil after to create a sharp line. Once you have located all the machined holes and edges, break the scissors out and cut. I found a hold lunch being the easiest method for the mounting holes and dowels.
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That's what you end up with. Essentially, you're making a gasket for the mating surfaces. I know the hole punch wasn't the best tool for me here, all I had was the giant one and couldn't find the handheld mini. Regardless, you get the point.

Take the "gasket" and lay it over the M3 bellhousing:
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Now take the "gasket and lay it over the M5 bellhousing:
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Oh, would you look at that! They're identical.

As soon as I have the shift component locations milled into the SMG bellhousing, I'll update the thread with a reassembly process for the M5 trans into the M3 housing. I also ran an equivalency search for all seals and parts between both versions of the 420G, happy to report that I haven't found any differences. Great news for availability as parts for the M5 can be difficult to find in comparison to it's little brother, M3, counterpart.

I encourage those wanting to do the 6 speed swap in their E46 to search for E39 540I or M5 transmissions as they're relatively cheap compared to the M3 version and the 540I version can be found in almost any recycler's lot. Of course a M3 bellhousing will be required, but you can always go the route of a conversion/adapter plate. But put it this way, the trans ran me 220$ (clutch package, mounts, shifter assy, crossmember and all were included in the purchase), the bellhousing 150$, I haven't priced out the machining costs but my guess is around 100$ to have the 3 holes milled out with mild milling for the circling, replace all seals 70$. For around 550$, you have yourself a bullet proof 6 speed trans for your car. I will be installing delrin carrier bushings, short shifter, DSSR, lightweight 14lbs flywheel and street strip clutch package.

Don't be afraid to try things and be creative. All the information you find online was discovered by someone who took a risk, physically or financially, at some point. Don't rely on others to do all the work for you, it will be your turn one day, and no one will give you the answer, you'll have to work for it. So start today...

If you have any requests for pictures, measurements, etc, please post them for all to see and I'll get them as the process goes on.

** I have been asked by a few members in the first couple of minutes of the thread being posted, asking if I would sell the trans once completed. Short answer, YES. I'm debating swapping a 1jz or RB25 for more power and reliability. If I decide to go that route, I will liquidate all my performance parts for the M52/54 with both transmissions (5 speed assembly and M5/3 converted trans) and all. Decisions, decision...


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Old 07-26-2014, 01:11 PM   #2
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interesting info, sub'd to see how this turns out GL
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Old 07-26-2014, 02:56 PM   #3
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UPDATE:

Here's the transmission with the M5 bellhousing:
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Here's the SAME transmission with the M3 bellhousing:
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Confirmed! Off to the machine shop this week


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Old 07-26-2014, 03:55 PM   #4
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Old 07-26-2014, 04:13 PM   #5
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This is very exciting.

I appreciate the quality research.
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Old 07-26-2014, 08:17 PM   #6
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Old 07-26-2014, 09:37 PM   #7
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Thanks for the support guys. One way or another, the work will pay off. Plus, it's fun as hell.

Only wish I had the time to fab a shift drum with modified selector forks to convert it to sequential. I might take the time and polish the gears and the housing's inner walls.

Progress to come shortly, I'll show how to strip the old bellhousing of the shift parts, what needs to be machined on the M3 housing to make it all work, and how to reassemble.


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Old 07-27-2014, 10:38 AM   #8
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With the modified m3 bell housing, I'm guessing you will need an m3/e39 M5 shifter? Also, and m5 5 clutch?

This would be the most efficient way for those of us who have non-M track cars to get a "built" 6 speed...

The main concern I would have would be the 500$ shifter I already have, and the 800$ light weight fly wheel.. Factoring in those costs, the total cost jumps significantly. However, if its possible to re-use those parts.. This would be perfect.

And, you could probably make some cash on the side supporting people in this position that would prefer a bolt on solution.

I'm looking forward to your progress photos. If we can re-use our current connections to the trans, I'll likely follow you.
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Old 07-29-2014, 01:13 PM   #9
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Originally Posted by dakkon View Post
With the modified m3 bell housing, I'm guessing you will need an m3/e39 M5 shifter? Also, and m5 5 clutch?



This would be the most efficient way for those of us who have non-M track cars to get a "built" 6 speed...



The main concern I would have would be the 500$ shifter I already have, and the 800$ light weight fly wheel.. Factoring in those costs, the total cost jumps significantly. However, if its possible to re-use those parts.. This would be perfect.



And, you could probably make some cash on the side supporting people in this position that would prefer a bolt on solution.



I'm looking forward to your progress photos. If we can re-use our current connections to the trans, I'll likely follow you.

As for the shifter, you can use whatever shifter you already have, but the shifter rod and shifter carrier will need to be sorted. The 6 speed is 3-4" longer than the 5 speed, so a shorter carrier and shorter linkage will be required.

The flywheels are all the same for these cars, only difference is the 10 or 11 spline clutch disk. Retain the flywheel, swap out the disk, retain flex plate, etc.

Driveshaft will need to be shortened and modified. Shortened because the trans is longer (as mentioned above) and the driveshaft because the 330 and M3 use a bigger guibo than the latter. Now that's really simple to sort out having either a custom aluminum guibo made to retain the bigger output shaft flange and smaller diff flange OR have a aluminum adapter made to convert the 3 bolt output shaft flange to a standard 4 bolt Nissan yoke for a one piece driveshaft. Would be so much easier if the 420G used a slip yoke output shaft.

The crossmember needs to be sorted as well; do we use the 6 speed M3 version or do we use the non M 5 speed and add a plate for the mounts? Can't speculate until later on.

Supporting parts to swapping this trans will require minor mods. You can get an idea of what will be required by simply looking at the M3 hardware (carrier, dssr) and figure that your carrier will be shortened and the dssr bent and shortened. As for any car, I always suggest a 1 piece driveshaft for serviceability, strength and ease of installation.


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Old 07-29-2014, 01:15 PM   #10
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Read the thread title and literally said 'huh?' out loud
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Old 07-29-2014, 01:23 PM   #11
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UPDATE 29-07-2014:

As I thought, my machine shop is close this week. It's the second week of the "Construction Holidays" here in Qc, where the incompetent and overpaid construction crews lay off for two weeks. Everything manual labour shuts down as well. So I won't be heading to the machine shop until next week. Hopefully I'll get the M5 bellhousing stripped before my sisters wedding this weekend, I'll post pics of the tear down if I do.

I've been doing some research on something pretty odd, but ingenious: mating a 1/2JZGTE to the M3 6 speed. ABC-Clutch in Latvia makes an adapter plate kit to make it happen. They're kit includes a crazy Tilton twin disk and LWF and all the bits to make it work. Problem is the 1900$EU... The plate alone is 450$EU. I've been talking with Roberts, an engineer at ABC and he's shared tons of info in the swap.

Now, the adapter plate is reasonable for what it is, but that clutch kit is way too insane, so I contacted David Norton from Spec Clutch NA with a custom flywheel and clutch design to make the 1/2JZGTE, adapter plate and M3 box, work together. He has confirmed that they could easily make it, just need to send them certain details. That's great news, I've been thinking of the swap for some time now. Can't start fantasizing too much quite yet, need to finish the trans build first.

Keep you all posted in the stripping of the housing in the next few days. Questions or comments always welcome, post below.

Cheers guys


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Old 07-29-2014, 01:26 PM   #12
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Read the thread title and literally said 'huh?' out loud

And after reading the first few posts, followed the "huh?", with "That's awesome, and I need one".


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Old 07-29-2014, 01:27 PM   #13
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And after reading the first few posts, followed the "huh?", with "That's awesome, and I need one".


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....same
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Old 07-29-2014, 01:27 PM   #14
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Very cool. http://losangeles.craigslist.org/lgb...558085983.html here's a 540 6 speed trans for $850 us. pretty pricey still but a unique swap for sure. for simplicity's sake i'd just use a 330 6 speed tranny.
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Old 07-29-2014, 01:34 PM   #15
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Old 07-30-2014, 12:02 AM   #16
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Very cool. http://losangeles.craigslist.org/lgb...558085983.html here's a 540 6 speed trans for $850 us. pretty pricey still but a unique swap for sure. for simplicity's sake i'd just use a 330 6 speed tranny.
Trust me, search around a bit and you'll find plenty for half of that. I've seen rebuilt units for 1000$USD.

The 330 6 speed ZF trans isn't as strong as the Getrag unit, and if you're going to do a 6 speed swap, why wouldn't you go with the stronger of the 2 units? You'll have to change the shifter assembly, driveshaft and clutch disk anyways, since you're doing that, going slightly further for a better system is a no brainer.
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Old 07-31-2014, 01:01 PM   #17
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UPDATE 31-07-2014:

Yesterday afternoon, I started stripping the M5 bellhousing... GRRRRRR! That really went poorly to say the least. I was able to extract more of the parts intact without problems, except a few that decided to be more of a problem than a teenage girl dumped at prom.

I was too pressed for time (and too pissed) to take proper pictures of the entire deconstruction, but will document it properly on Sunday upon my return from the wedding.

I did discover a few interesting things during the disassembly though. Almost every part inside the transmission (gears, synchro blocks, bearings, gears, etc) have BMW part numbers laser etched into them. I'll take tons of pictures and document them properly. I'm heading to the shop shortly, at which point I'll bring the camera and get it all. I'll take pics of the parts that decided to sh*t the bed and what I'll have to do to rectify the problems. Generally speaking, braking a pin isn't a big deal, call the local rebuilder for a spare and bingo. But thanks to no after sale support from BMW or Getrag, that small broken pin represents a headache. We'll find a fix. Whoever will get this transmission after will have a bulletproof rebuilt M5 unit for our I6 cars.

Should I turbo the 323? Something small like a GT2871R in .84 trim at 6-7 psi. Issue would be the tuning, unles you go the way of the AEM EMS at 3k. Too many choices... None are easy, all sound tempting

Pics to come today, thanks for the support guys
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Old 07-31-2014, 01:22 PM   #18
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Originally Posted by drift.mechanic View Post
Trust me, search around a bit and you'll find plenty for half of that. I've seen rebuilt units for 1000$USD.

The 330 6 speed ZF trans isn't as strong as the Getrag unit, and if you're going to do a 6 speed swap, why wouldn't you go with the stronger of the 2 units? You'll have to change the shifter assembly, driveshaft and clutch disk anyways, since you're doing that, going slightly further for a better system is a no brainer.
What's the need or obsession with all this strength? I'm sure that strength doesn't come free. Now you've increased your rotating mass, mechanical drag, and overall weight for what? There's a reason cars come with the transmissions they do.

Unless you are doing a Veyron engine swap then I understand
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Old 07-31-2014, 02:01 PM   #19
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What's the need or obsession with all this strength? I'm sure that strength doesn't come free. Now you've increased your rotating mass, mechanical drag, and overall weight for what? There's a reason cars come with the transmissions they do.

Unless you are doing a Veyron engine swap then I understand
There will be no increase in rotating mass, if anything, a decrease by using a 14lbs flywheel which would dump 22lbs (roughly) in rotating assembly mass. I can use the OEM DM flywheel with a different clutch disk to retain OEM weight. Since Ive never been a fan of the DM design, when it comes time to install, I will swap out.

Increased overall weight, yes but only slightly. I dont have the official weight numbers of both boxes, but willing to bet theyre within 15lbs of eachother. 15lbs is negligible and would simply offset the weight savings of the 14lbs flywheel (but the benefits of the -22lbs of rotating mass would still be evident).

The power loss from mechanical drag on the extra gear (6th) would be fractions of 1% increase. Until locked in use by the synchro box, the main shaft 6th gear spins in unicen with its output shaft mate. If the overall power loss from a RWD manual box is 8%, I cant see a reason it would even be a factor. With the addition of a one piece driveshaft, eiminating the center hanger bearing and both its yokes, the 1% (+/-) has been compensated for.

But thats not the purpose of this thread. Thanks to BMW and its lack of proper final ratios and LSD, the NON M folk are stuck seeking an M3 rear end as the cheapest LSD option. Swap a 3.64 (lowest LSD gear in the M3) and highway driving will be come a nightmare. 3.92 and 4.09 even worse. How to compensate, add the 6 speed box. Pay 1600$ for a 6 speed box in unknown condition isnt something we want to be doing, so now with simple tooling and a bit of recycler searching, you can build a 6 speed for fractions of the cost to buy one outright.

Adding driveline strength is always a bonus. My 5 speed has small issues, the shift between second and third often skips the 3rd speed gate. On occasion first gear even launches out when the car starts to move. Im tired of the problems and this 6 speed swap, once completed and installed, will eliminate all those small hiccups.

(sorry for the grammar mistakes, Im using a french keyboard)

---------------------------------------------------

Pics to come this afternoon, heading to the shop soon.
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Old 07-31-2014, 02:08 PM   #20
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Originally Posted by drift.mechanic View Post
There will be no increase in rotating mass, if anything, a decrease by using a 14lbs flywheel which would dump 22lbs (roughly) in rotating assembly mass. I can use the OEM DM flywheel with a different clutch disk to retain OEM weight. Since Ive never been a fan of the DM design, when it comes time to install, I will swap out.

Increased overall weight, yes but only slightly. I dont have the official weight numbers of both boxes, but willing to bet theyre within 15lbs of eachother. 15lbs is negligible and would simply offset the weight savings of the 14lbs flywheel (but the benefits of the -22lbs of rotating mass would still be evident).

The power loss from mechanical drag on the extra gear (6th) would be fractions of 1% increase. Until locked in use by the synchro box, the main shaft 6th gear spins in unicen with its output shaft mate. If the overall power loss from a RWD manual box is 8%, I cant see a reason it would even be a factor. With the addition of a one piece driveshaft, eiminating the center hanger bearing and both its yokes, the 1% (+/-) has been compensated for.

But thats not the purpose of this thread. Thanks to BMW and its lack of proper final ratios and LSD, the NON M folk are stuck seeking an M3 rear end as the cheapest LSD option. Swap a 3.64 (lowest LSD gear in the M3) and highway driving will be come a nightmare. 3.92 and 4.09 even worse. How to compensate, add the 6 speed box. Pay 1600$ for a 6 speed box in unknown condition isnt something we want to be doing, so now with simple tooling and a bit of recycler searching, you can build a 6 speed for fractions of the cost to buy one outright.

Adding driveline strength is always a bonus. My 5 speed has small issues, the shift between second and third often skips the 3rd speed gate. On occasion first gear even launches out when the car starts to move. Im tired of the problems and this 6 speed swap, once completed and installed, will eliminate all those small hiccups.

(sorry for the grammar mistakes, Im using a french keyboard)

---------------------------------------------------

Pics to come this afternoon, heading to the shop soon.

So you're using a stronger gearbox as you say with stronger internals as you say.

Internals=gears.

So these gears, being stronger, don't have increased weight or rotating mass, and don't have additional mechanical drag due to more gear (surface) area acting on one another? I mean the gearbox was made for a 400hp M5 (which is why it can handle more torque)

Not trying to rain on your parade, just wondering what the obsession is with more strength for your 323. You do know that the ZF 5-speed manual is often used on E46 M3s in race situations right? As well as F/I applications. So why is the increased strength of a M5 gearbox so important for your 323?

Also are you certain that the ratios designed for a V8 M5 match your 323 engine's power delivery characteristics?

Sometimes it's good to do research and make careful decisions rather than just upgrading for the hell of it.
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