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

[Singing6]

BMW E34 525i (M50) 6-Speed swap guide

It is fairly well documented that the Getrag g250 in 93-95 525i/5’s is weak. I have read many a post where power was added and then transmission breaks. The ZF 310 in the 92 525i/5 is known for being much stronger. Most of the reason for me doing this swap was to have a transmission that can take more power (M50B30 stroker in the short term, boost in the long term). The other reason was to have a nice highway gear. As far as I can tell, my car is the first DOCUMENTED swap of this trans into a 525i E34 (completed 9/13/2019). If you find one earlier, keep it to yourself, my ego will appreciate it!

Preface:
All M5x gen engines have the exact same bolt pattern for the bellhousing. (Up until a revision on the m57’s) The M50 and M20 also share a bolt pattern but the M20 is placed in the engine bay much closer to vertical than the M50 because it is not as tall as the M50. This means to bolt up an M20 trans to an M50, you have to rotate it over. In short, you can bolt the m57 from an e39 530D onto a 1977 E12 520 manual. This is a swap I very much want to see done. But either way, that is a 30 year range to pull direct bolt on transmissions from.

There are two easy choices to swap a 6 speed into a 525. One is the Getrag 420g from the E46 M3 (make sure it is not an SMG trans, that one needs some work to work). The other is the ZF GS6-37bz from all manual E46 330’s produced after 3/2003, all manual M54 E60’s produced after 3/2003 (until they switched to the n5x), and all manual M54b30 Z4’s produced after 3/2003. The ZF GS6-53bz will also bolt up to the M50 but it requires much more creativity to get a working flywheel because that is an N54 trans (now hearing this is iffy, working on confirmation)

I chose to use the ZF GS6-37bz because it is a fair bit cheaper to get ahold of than an M3 420g. It is also fairly rare because of the short time it was used.

There are 4 main areas to look at when swapping in a transmission that is not stock:
-Clutch mechanism
-Transmission mounting
-Driveshaft
-Shifter mechanism


Clutch Mechanism:

This one is pretty easy. Get the clutch and flywheel from an E46 330. The Flywheel for the ZF 6-speed is unique from earlier BMW flywheels because the input shaft is now shorter. The pilot bearing is in the flywheel instead of the end of the crankshaft. The stock E34 M50 starter will work fine with the M54 flywheel (there were some nights of lost sleep over that one).

Pro tip is to change out the plastic clutch fork pivot for a metal one. Used an AKG brass pin and had to sand down the tapper to fit. My recommendation is to use 120 git sand paper and twist the tapered end of the pin in it. Do this for a little bit and check fit. Then sand some more until you are within a hundredth or so inch of flush (use a feeler gauge) with the case. Put some locktight on the tapered surface and tap it in with a deep socket. Be careful, many a transmission bellhousing has been cracked by trying to force these metal pins into the trans.
(2021 me talking here: don’t ever get the brass pins. They wear out fast. Get the stainless steel ones)


Also, when you get the clutch kit, you may notice that the throw out bearing has two orientations that it can go in (you will understand what I am saying if you see it). It goes in the shorter position. (SEE FIGURE 1)

For the clutch slave I found some delightful info! Perusing RealOEM I discovered that the clutch slave used in 93-95 e34 525i/5’s is also used in E60 530’s made after 3/2003 (does that number look familiar?). That means that you can use the stock Getrag g250 slave (my car was a 95 525i/5, thanks to this it is now a 525i/6). I would recommend replacing it with new and changing the clutch slave hose as well but watch out because the fluid likes to pour out when the system is open, it is not like removing a brake hose.

I am using the Self-Adjusting-Clutch pressure plate. I can tell you that it was not fun to install (my retainer thingy popped off unexpectedly, but I have a friend at BMW who was able to bring over the special tool to save my ass). It also results in a VERY LIGHT clutch pedal. I am looking into ways to stiffen this back up or get a non-SAC pressure plate in the future (looking your way Moroza). (2021 me: read post #35)


Transmission Mounting:

The 37BZ is about as long as the automatic in the 525iA (M50). And by “about” I mean close enough to use the 525iA transmission crossbrace.

The problem you will encounter is that the trans mount locations on the 37BZ (when pulled from an E46 at least) are too low. They need to be raised by 40mm (iirc) to fit in the older BMW’s like the E34 and E36. Thankfully the E36 group (gaggle of pre-pubescent teenagers) comes to the rescue here by having pre-made parts you can just order. I used the Reboot Engineering adapter bracket that replaces the bracket bolted to the back of the 37BZ to raze the mounts up to the necessary height.

Another thing to note for 525i people; the manual (Getrag g250 and ZF 310) and automatic (A4S) have forward transmission mounts where the engine and transmission meet. These will not be used on the 37BZ because the trans does not have provisions for the mounting points. This means there will be more load on the rear mounts. I found that even with brand new engine and transmission mounts, the back of the trans could move A LOT. I put in Rouge Engineering rubber transmission mounts (had to grind down the studs a lot to fit) to control this movement. You could run E36 hourglass trans mounts if you wanted to stay OEM, they would be somewhere in between the stiffness of the rectangular E34 mounts and the Rouge Engineering mounts.

Lastly, I found that the clearance between the top nuts for the transmission mounts and the driveshaft flex disk (giubo) what very small (I measured 0.019 inches at closest approach) so pay attention to what nuts you use if you get the Reboot Engineering adapter (I used Genuine BMW hardware on this entire project unless specified otherwise, so that always works).

The reverse switch connector on the trans is the same as on the E34 loom so don’t worry. The connector is on the right side of the 37BZ and the left side of the g250 so you will have to cut some Zipties and move the wire but that is it. This is the only electrical thing you have to touch in the entire project (other than disconnecting the O2 sensor for exhaust removal) so for those of you that are useless with electrons: you’re safe for now.


Driveshaft:

The 37BZ is a bit over 5 inches longer than the g250. Enough that many people can confuse it with an automatic. As mentioned before, it mounts using the 525iA (M50) transmission crossbrace so that gives you a rough idea of length.

For my driveshaft I got a E34 530/5 (M60 for those of you in Europe that have 530/5 M30’s) because the rear half is identical to a 525i/5 but the front half has the larger flex disk (giubo) for the V8 trans. This is important because the 37BZ also has the large giubo.

I then had it shortened by 5.5 inches at a driveline shop (and balanced of course). The actual math came out to 5.56 inches iirc. This cost me around $350 but part of that was because this shop worked only in SAE and so had to replace the tube with one in US units. I also had them put in my new CSB while they were at it.

The distance you need to measure is from the U-joint at the middle of the driveshaft to the surface of the driveshaft that mates with the giubo. Then measure the driveshaft side of the giubo to the bellhousing of the transmission. Do this for your old transmission and driveshaft and then the new transmission and driveshaft and you will know how much to adjust by. You have some margin for error here so don’t fret (like I did) and think you need to get it perfect. An 1/8^th of an inch error is nothing to worry about. To get a sense of the margin, look at how long the slots on the center support bearing (CSB) are and how much the constant velocity (CV) joint at the back of the driveshaft can move by; that is your margin.

Someone has mentioned to me that shortening the 530/5 driveshaft by 5.5 inches brings it within 2mm of the length of the 530iA (still M60) driveshaft. If the CV and giubo are still the same diameter and bolt spacing as the 525/5 diff and 37BZ trans, it will bolt in. (2021 me: the shaft that bolts in is the pre-10/93 530iA shaft, with the e36/46 m3 flex disk. Just get that from the start, see post #35)

Pro-tip: remember that the front and rear halves of the driveshaft are balanced together. They need to go together in the exact same orientation that they were balanced in otherwise they will shake very badly.


Shifter Mechanism:

The transmission I picked up was from an E46 so those are the shifter parts I started with. If you get a 37BZ pulled from an E60 or Z4 this info likely will not apply.

Before doing anything else, remove all the wearable items from the 37BZ and throw them in a bag (throw out the bag once the swap is done). Order all new parts. Also replace the shift selector shaft seal and change the transmission fluid. After a fair bit of searching, I went with Genuine BMW LL-02 fluid. I also did oil analysis on the old fluid and discovered it only had 28k miles on it. This is a great way to find out some service history of your new transmission, especially if, like me, the seller you got it from knew nothing about it. These transmissions do not have the shift detent issues that the older ZF 310’s (and 320’s?) have, so don’t worry about that.

I was already running the Garagistic poly rear shifter mount for the E34. I also ordered their Delrin mounts for the oval bushings in the shift support arm. I have not loved them but Garagistic is sending me new ones that are more of an interference fit so I will get back to you on this. (2021 me: they suck. See post #35)

To get the E46 Shift Support Arm (SSA) and Single Shear Selector Rod (SSSR) to work with the E34 I had to add 1 ¾ inches between the transmission and the ball joint for the shifter arm. (SEE FIGURE 2)

When welding the SSSR, note that it is stainless steel, I briefly flipped out when it started turning funny colors while I was welding some scrap steel rod to it.

The stock SSSR works fine but I have Garagistic making me a custom DSSR out of stainless steel to get an even tighter feel in the shifter. Also have a Schmiedmann adjustable shifter arm that is going in when that arrives. I will report back on this. (2021 me: the shifter arm is ok, the Garagistic DSSR sucks. See post #35)

The SSA is aluminum so if you don’t have a TIG welder and the skills to use it, expect to pay someone else to weld this because I don’t know of anything on the market for this part that is a bolt in. I did have to cut ½ an inch off the spike at the end of the SSA to get it to fit right in the rear shifter mount. (2021 me: dont bother welding these support arms. The metal is just too pourus)

If the Delrin mounts from Garagistic (mentioned above) don’t end up being to my liking I will be machining out a billet SSA on the CNC machine that no longer has any bushings at the interface with the transmission. It will just be small holes in the arm for the two “bitch clips” (yea, have fun. There are two of them now, but I would say they are less difficult than the old one).

The E46 shifter arm has been working great for me so far, but I also prefer a long throw in the E34. It just seems right in such a big car. But as can be seen from the parts I am using, that is no excuse for slop of any kind.

Lastly, for the shift knob I am making something special. I will update as it comes along, but I am making a FULLY wood knob that is illuminated with the 6-speed emblem that has the ///M color stripe in the top left. This is not a knob that BMW ever gave us, but I want to make it. I have an old 5-speed knob but all the clear coat is chipping off and so I have to strip it and re-coat after dremeling it out for the illumination components from another BMW knob.

Ok, that is it for the different systems. I skipped over a bunch of little stuff because it should all be covered in the Bentley manual and other places for normal clutch replacement jobs. Stuff like how to mount the guibo and how to install the SAC clutch.


How does it drive:

The 37BZ is much more notchy (in a good way). Combined with the 3.46LSD I swapped in in prep for this transmission, 6^th gear feels a little taller than 5^th was with the g250 and 3.23LSD. In a perfect world I would probably run a ratio in the middle of these two. I believe 3.38 out of the E36 is the closest to that but have not looked so feel free to chime in.

As mentioned before, the clutch pedal is very light and bites lower down than I am used to but my old clutch was also on its last legs so…..

All in all, it feels stock. These are not my words; these are the words of the 5 or so people I have let drive it since completion.

I can confirm that it does burnouts well.


Additional notes I did not know where to put:
-Change all your exhaust hardware. Buy all of it new ahead of time because you should expect EVERY nut, bolt, and stud to snap during removal.

-Have friends over. It is fun

-Change your O2 sensor, it is a 60k mile wear item on E34’s according to BMW

-I did this entire swap on jack stands in what was for all intents and purposes, a single bay garage. It should be noted that it had heat and AC.

-The dowel from the starter to the transmission bellhousing will occasionally get fused to one or the other. Use penetrating fluid and patience; it will come out.

-If using the SAC pressure plate, have a contact ready in case it proves “difficult.”

-Expect the old transmission crossbrace to body bolts to break when you go to remove them. 3 out of the 4 broke for me, but I did not notice there is a cutout above the crossbrace in the body where you can spray penetrating fluid on the body nut so give that a try.

-I left the old pilot bearing in the crank because there was no need to remove it. It will slowly eat away at my mind until I remove it. (2021 me: I removed it)

-The 6-speed flywheel uses different bolts than the normal flywheels. The bolts are much shorter and $8 a piece from BMW. Have fun.


2021 me: made a full parts list see post #47 for more info, but here is the link:

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



Figure 2.jpgFigure 1.jpg
Figure 2 and 1 respectively

Already working on the next crazy thing,
Singing6

[dannyzabolotny]

How much did this project cost you in total? And also, would it be easier to use a 420g with a straight-6 bellhousing? I have a V8 420g and know of a guy that sells E46 M3 manual bellhousings, so I could make that work too.

[moroza]

All M5x gen engines have the exact same bolt pattern for the bellhousing. This means you can bolt an M50NV to the transmission in a 2007 X5 diesel. The M50 and M20 also share a bolt pattern but the M20 is placed in the engine bay much closer to vertical than the M50 because it is not as tall as the M50.

Not quite. The M57N2 has a different boltpattern than the M57, and M57N1 is unclear (source). The difference can supposedly be solved by drilling. Early M57 are shared with M47 which is known to fit (search for Wanganstyle's 37DZ swap threads) with a couple of bolts omitted. Also, the diesels are more vertical than the M5x gassers. While it's likely that the M51 boltpattern is compatible, I've yet to see hard evidence.

bellhousings.jpg

There are two easy choices to swap a 6 speed into a 525. One is the Getrag 420g from the E46 M3 (make sure it is not an SMG trans).

The SMG can be modified (~$300 of machine work and random parts) to be a manual. This is a relatively common thing and apparently results in an above-average (for shift feel and synchro life) manual transmission.

The other is the ZF GS6-37bz from all manual E46 330’s produced after 3/2003, all manual M54 E60 530’s produced after 3/2003, and all manual M54b30 Z4’s produced after 3/2003.

Emphasis on "M54". To be clear, the 37BZ fitted to N52 (E9x and later E6x) is NOT the same transmission as the M54 box. Boltpatterns are different; it's unclear by how much. However, a related piece of data is that the 53BZ fits the N52 if a couple of holes are slotted out and one bolt omitted.

Also the M54 E60 525 had the 37BZ, according to RealOEM.

The ZF GS6-53bz will also bolt up to the M50 but it requires much more creativity to get a working flywheel because that is an N54 trans.

I've seen "the 53BZ should bolt up, I think", and "the 53BZ does not bolt up, I tried" (and someone claims this to the extent that they make and sell an adapter plate), but never seen "the 53BZ does bolt up, possibly with minor work, I tried".

There is also a rare version of the 37BZ that shares its boltpattern with the M54, but has a longer input shaft to fit an S54 flywheel. It was fitted to the Z4M.

The Flywheel for the ZF 6-speed is unique from earlier BMW flywheels because the input shaft is now shorter. The throw out bearing is in the flywheel instead of the end of the crankshaft.

Pilot bearing, not throwout bearing.

I am using the Self-Adjusting-Clutch pressure plate. I can tell you that it was not fun to install (my retainer thingy popped off unexpectedly, but I have a friend at BMW who was able to bring over the special tool to save my ass). It also results in a VERY LIGHT clutch pedal. I am looking into ways to stiffen this back up or get a non-SAC pressure plate in the future (looking your way Moroza).

E34 M50 clutch slave 21526775924 has a 22.2mm bore and is used on both early ZF 310Z and later Getrag 250G transmissions. E36 M3 used it too.
E46 M54 slave 21526785966 also has a 22.2mm bore and is used on both 5- and 6-speeds.
E36 M52B28 slave 21521159045 has a 20.6mm bore and would stiffen up the pedal. Seems like all E36 use it except the M3.

The longer I stare at pictures of the flywheels and pressure plates for an 37BZ-M54 and early M52B28, the more they tease me, "We might just bolt up!" I wonder if anyone's tried the 37BZ-M54 flywheel and friction disk with M52B28 pressure plate? They look close enough that unless someone says "I tried it and the answer is no" or some other hard data why they won't work, I'm willing to deal with the labor and return shipping of finding out first-hand.

because the rear half is identical to a 525i/5 but the front half has the larger flex disk (guibo) for the V8 trans. This is important because the 37BZ also has the large guibo.

E34 530i and 525i (both regardless of transmission) use 96mm giubo (not guibo) 26117511454. EDIT: except 525iM from 7/92, which used 78mm giubo. There is an output flange 23217641246 from a later 37DZ (diesel) that fits a 105mm giubo like the 540i, though with 12mm bolts instead of 14mm.

I then had it shortened by 5.5 inches at a driveline shop (and balanced of course). The actual math came out to 5.56 inches iirc. This cost me around $350 but part of that was because this shop worked only in SAE and so had to replace the tube with one in US units. I also had them put in my new CSB while they were at it.

RealOEM quotes an E34 530iA driveshaft from 10/93, using an 80mm CV at 1521mm. This thread gives 530iM shaft length at 1663mm. 5.56" = 141mm. 1663-141=1522, strongly suggesting that a stock 530iA driveshaft will fit a 37BZ in an E34 with 80mm CV, assuming the measurement reference points are the same.

If the CV and guibo are still the same diameter and bolt spacing as the 525/5 diff and 37BZ trans, it will bolt in.

They are both 96mm giubo and 86mm CV. Some (all?) 525iA had 80mm CV.

Regarding trans mounts: M6x uses only two motor and two rear trans mounts 23701141614. Some E34 M20, M21, and M51 (mostly autos) used them as well. IME they are (barely) adequate for an M62.

Also replace the shift selector shaft seal

Yes! This is *FAR* easier when the trans is out, and is a common leak point. BMW 23117531360 is ~$25. National 710714 has the same dimensions 15x21x5.

How much did this project cost you in total? And also, would it be easier to use a 420g with a straight-6 bellhousing? I have a V8 420g and know of a guy that sells E46 M3 manual bellhousings, so I could make that work too.

This doesn't work. While the bellhousing bolts on, the input shafts are different between the V8 and L6 420G. Swapping them requires some serious equipment and know-how. Also, swapping cases could mess up bearing preload.
https://www.bimmerforums.com/forum/s...rchangeability
https://forum.e46fanatics.com/showthread.php?t=1046393

[Hofmeister]

I've seen "the 53BZ should bolt up, I think", and "the 53BZ does not bolt up, I tried" (and someone claims this to the extent that they make and sell an adapter plate), but never seen "the 53BZ does bolt up, possibly with minor work, I tried".

a well known member of the turbo e36 community bolted one up by just enlarging one hole, idk if theres a thread here but he has a post on FB boosted e36 world. id like to link but its a closed group

[Singing6]

Moroza, that behemoth will take a bit of time for me to respond to but it is packed with amazing information. I have a contact on the facebook groups who is running a 53bz on his 525. I will ask for pics to confirm adapter or no.

[Singing6]

E34 M50 clutch slave 21526775924 has a 22.2mm bore and is used on both early ZF 310Z and later Getrag 250G transmissions. E36 M3 used it too.
E46 M54 slave 21526785966 also has a 22.2mm bore and is used on both 5- and 6-speeds.
E36 M52B28 slave 21521159045 has a 20.6mm bore and would stiffen up the pedal. Seems like all E36 use it except the M3.

I had both the e46 m54 slave and the e34 slave on hand. The M54 slave would be tricky to get plumbed up as it would require a custom hard line.

I chose to use the e34 slave because it meant that I did not have to change anything (I still did replace the hose and slave with new, but still stock, parts).

It looks like the 20.6 mm bore version still has the port in the e34 location so I will have to give that a try.

BTW, does anyone want a NIB FTE e46 M54 6-speed slave? Or the soon to be available 22.2mm bore e34 slave that has under 1k miles? I can cut you a good deal!



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[Singing6]

There is also a rare version of the 37BZ that shares its boltpattern with the M54, but has a longer input shaft to fit an S54 flywheel. It was fitted to the Z4M.

More info on this please. This could be a solution to the SAC pressure plate choices. Now all we have to do is fine one of these suckers!

(2021 me: you do NOT want that trans. Yes it has the longer input shaft of the g420, but it does NOT share the g420 10T spline. It still uses the 22T spline of the 37bz. Making the clutch for that trans an honest to god unicorn part.)

[Singing6]

Regarding trans mounts: M6x uses only two motor and two rear trans mounts 23701141614. Some E34 M20, M21, and M51 (mostly autos) used them as well. IME they are (barely) adequate for an M62.

These are the same thing as the E36 hourglass mounts I mentioned here:

You could run E36 hourglass trans mounts if you wanted to stay OEM, they would be somewhere in between the stiffness of the rectangular E34 mounts and the Rouge Engineering mounts.

In fact, looking at pictures of the two, I cannot tell the difference between 22316799331 (E36 M3 and everything after) and 23701141614 (the V8 E34, E32, E31, and M51 E36). So on the fact that the parts that each of us is talking about, I have to say I agree with you!

[Singing6]

How much did this project cost you in total?

Not a number I particularly want to find out but I will say it took me about 14 months to acquire all the parts (tighter budget so went slow) and including things like the 3.46LSD swap that was done directly in prep for this, I would guess the number is around $3500.

The part that made me happy is that, including the cost of the Rouge Engineering trans mounts, the cost of unexpected parts that had to be ordered after starting the swap was under $100! It was 4 transmission crossbrace bolts, one exhaust header-to-downpipe stud, and those rubber mounts.

I am not counting the shifter parts because they are not NEEDED, just wanted. The car is driving fine without them.

[moroza]

What is your opinion of the flywheel weight?

a well known member of the turbo e36 community bolted one up by just enlarging one hole, idk if theres a thread here but he has a post on FB boosted e36 world. id like to link but its a closed group

Moroza, that behemoth will take a bit of time for me to respond to but it is packed with amazing information. I have a contact on the facebook groups who is running a 53bz on his 525. I will ask for pics to confirm adapter or no.

These are M5x motors? Let's see the data!

I had both the e46 m54 slave and the e34 slave on hand. The M54 slave would be tricky to get plumbed up as it would require a custom hard line.

Does it not have a standard female M10x1.0 DIN/ISO bubble flare port? Oh, it points the other way and is otherwise no better?

Would you be so kind as to measure the M54 slave's rod length and travel? And if you have any other slaves, same for them?

...Or the soon to be available 22.2mm bore e34 slave that has under 1k miles? I can cut you a good deal!

Quite possibly. Depends on what clutch I end up using (still debating, but will probably give the B28 setup a try). What brand?

More info on this please. This could be a solution to the SAC pressure plate choices. Now all we have to do is fine one of these suckers!

http://www.m3forum.net/m3forum/showt...=480118&page=2

These are the same thing as the E36 hourglass mounts I mentioned here:
In fact, looking at pictures of the two, I cannot tell the difference between 22316799331 (E36 M3 and everything after) and 23701141614 (the V8 E34, E32, E31, and M51 E36). So on the fact that the parts that each of us is talking about, I have to say I agree with you!

They could be significantly different stiffnesses.

[Singing6]

In regards to flywheel weight, it is not perceptibly different from the stock M50 flywheel. I have heard Dinan makes a lightweight dual mass but this also apparently costs $2k. (2021 me: I didn’t notice the weight for a while. It is slight, but heavier for sure. The Dinan flywheel is NLA)

Clutch chatter was not acceptable for this build so I stuck with the dual mass. I do wish it was 10lbs lighter.

The contact that did the 53bz swap may be making an account here because of this thread but in case he does not I will quote him:

Me: “Does the 57bz require an adapter?”

Him: “No*

But the asterisk is where pictures come in handy. You really don't want to use an adapter here as it just adds downstream cost”

I will measure the slave rod length of all the bits for you. I need to do a checkup on everything under the car this weekend anyway.

All the slaves I buy are FTE brand.

Good though on the stiffness, someone should get them side by side and find out.

In other news, the Garagistic DSSR just arrived. It looks pretty but I will be doing a slight mod to get it to a tighter fit. They said it would require filing down the shifter arm to fit but mine is a hair loose. I am going to complain to them and see what they want to do about it. They also only sent 2 of the 4 oval bushings they said they were sending. This is the first bad experience I have had with them so I will give them a break before I rage quit.


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[moroza]

Some data points I just acquired, mostly first-hand:

37BZ-M54 from engine side to giubo side is 635mm, measured at multiple points with a straightedge. To the trans-side studs of the mounts is ~615-630mm or a bit more (they are slotted).

A4S-310R is 750 +/- 3mm, measured installed in car but otherwise to the same standard. To the crossmember-side studs of the mounts is 655 +/- 3mm. That looks too far for the stock 37BZ rear mount. Did you drill additional holes in the crossmember, or does the aftermarket trans brace allow that much adjustment?

Driveshaft 26111227387 for a 4-speed M50 E34 with 86mm CV joint (EDIT: it's an 80mm CV. This probably changes the length) is 1390 +/- 10mm from diff side of CV to giubo side of front yoke, as installed. Dorman 946-986 claims to fit at 1384mm, but my numerous bad experiences with Dorman lead me to take anything they say with a grain of salt. If true, a 37BZ-M5x driveshaft for an E34 with 86mm medium-case diff input (EDIT: 80mm), using 96mm giubo 26117511454, should be approximately* 1505mm. This is significantly different from the 1521mm length we got on paper. Either 1. BMW's measuring points are different, or 2. the 5.56" lengthening is inaccurate, or 3. the 39mm difference between 525iM and 530iM shafts is inaccurate, or 4. Dorman's numbers are as garbage as their products AND my measurements of the driveshaft are as unreliable as the difficulty of measurement would suggest. All are plausible, but if you could doublecheck #2...

(*Because the CV can slide axially on the driveshaft, its rear mounting surface - where I measured - is only approximately where the driveshaft rear half ends. I'd guess the tolerance to be +/- 8mm, half of the length discrepancy.)

[Singing6]

Some data points I just acquired, mostly first-hand:

37BZ-M54 from engine side to giubo side is 635mm, measured at multiple points with a straightedge. To the trans-side studs of the mounts is ~615-630mm or a bit more (they are slotted).

A4S-310R is 750 +/- 3mm, measured installed in car but otherwise to the same standard. To the crossmember-side studs of the mounts is 655 +/- 3mm. That looks too far for the stock 37BZ rear mount. Did you drill additional holes in the crossmember, or does the aftermarket trans brace allow that much adjustment?

Driveshaft 26111227387 for a 4-speed M50 E34 with 86mm CV joint is 1390 +/- 10mm from diff side of CV to giubo side of front yoke, as installed. Dorman 946-986 claims to fit at 1384mm, but my numerous bad experiences with Dorman lead me to take anything they say with a grain of salt. If true, a 37BZ-M5x driveshaft for an E34 with 86mm medium-case diff input, using 96mm giubo 26117511454, should be approximately* 1505mm. This is significantly different from the 1521mm length we got on paper. Either 1. BMW's measuring points are different, or 2. the 5.56" lengthening is inaccurate, or 3. the 39mm difference between 525iM and 530iM shafts is inaccurate, or 4. Dorman's numbers are as garbage as their products AND my measurements of the driveshaft are as unreliable as the difficulty of measurement would suggest. All are plausible, but if you could doublecheck #2...

(*Because the CV can slide axially on the driveshaft, its rear mounting surface - where I measured - is only approximately where the driveshaft rear half ends. I'd guess the tolerance to be +/- 8mm, half of the length discrepancy.)

No holes had to be drilled in the 525iA crossbrace for it to fit. The crossbrace to body holes are slated at an angle and the Reboot Engineering mount is open facing the rear of the car so there is lots of wiggle room there.

As for #2: I gave the shop all of my raw measurements, calculated 5.5” number, and the driveshaft. We then talked through everything to have a second set of eyes on the data. They had to re-tube the driveshaft because there was not room on the ends to take out that much. They also only work in imperial (literal shed of a machine shop, run by ancient men, in the woods of MD, that do amazing work). They took out exactly 5.5 inches. What I will say is that making the shaft another ⅛” shorter would be nice, it is a tight fit to get the front half over the output flanges pin on the trans.

Will get you the driveshaft length when I next get under the car (doing a bunch of fuel system work soon so maybe then) and the clutch slave strokes. Differential equations has been kicking my ass as of late so car work has taken a back seat (but not car work planning, that never ends)


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[moroza]

Raw measurements would be groovy, including of the original 525iM driveshaft. PM sent regarding slave.

If memory serves, removing a stock E34 driveshaft involves slightly compressing the CV, not all the way, and the pin/bushing fit is no big deal. WAG is that your driveshaft is ~10-15mm too long, which would put it somewhat within the tolerances of my numbers.

[Singing6]

Raw measurements would be groovy, including of the original 525iM driveshaft. PM sent regarding slave.

If memory serves, removing a stock E34 driveshaft involves slightly compressing the CV, not all the way, and the pin/bushing fit is no big deal. WAG is that your driveshaft is ~10-15mm too long, which would put it somewhat within the tolerances of my numbers.

Don’t have the 525iM driveshaft anymore (sorry not sorry) or the g250. Traded them and my M5 front sway bar for a freshly powdercoated RD 27mm front sway bar. Which I would call a spectacular deal considering what the g250 is worth in my mind (about $100).

I definitely remember the 525iM driveshaft coming out easier than the custom driveshaft went in. I don’t recall having to lower the trans at all but I definitely had the CSB dangling at an odd angle with the CV fully on (nuts snug) the diff so be able to get the front of the driveshaft over the trans output flange centering pin.

Moroza, my advise to you is to get yourself the 530iA driveshaft along with the rest of the parts for the swap and see if it will fit on the car in person. Everything you are saying makes me think it is very close and should fit. If not, have it adjusted at a shop, it won’t take very much.


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[moroza]

Actually, I'm going to try an E28 driveshaft (not quite sure which) with two U-joints and a 4-bolt rear flange. U-joints cost a tenth of a CV and are refined enough for an E28 (and E34 520i and diesels). Furthermore, those driveshafts appear to have a lot more adjustment room in their splined section, and I'm counting on no driveshaft modifications required at all, possibly excepting a modified CSB. Cost aside, I have a below-average record of success with outsourcing, and strongly prefer to avoid it with factory parts if possible.

[E38740iMD]

im pretty sure andy can help out with the e28 driveshaft (south42) he may be able to measure if it he has one. he parts e28 all the time

[Singing6]

Actually, I'm going to try an E28 driveshaft (not quite sure which) with two U-joints and a 4-bolt rear flange. U-joints cost a tenth of a CV and are refined enough for an E28 (and E34 520i and diesels). Furthermore, those driveshafts appear to have a lot more adjustment room in their splined section, and I'm counting on no driveshaft modifications required at all, possibly excepting a modified CSB. Cost aside, I have a below-average record of success with outsourcing, and strongly prefer to avoid it with factory parts if possible.

I have a shop I can recommend if you need it. They did very good work.


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[moroza]

Two updates in my driveshaft info:

E34 525iA shafts appear to have 80mm CV, not 86mm. I edited my post above. This changes the lengths required.
E34 525iM used 80mm CV up to 9/90, 86mm from then.
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. Conclusion: 80mm CV takes a 10mm longer driveshaft.
E28 shaft (likely a >9/85 535iM) is too long even with the splines collapsed. Earlier (or maybe just MY 1985) 535iM are quoted at 1522mm and should work. The CSB would need a bracket built as it's ~8?-12?cm too far forward.
All 4-bolt models I could find (E12, E28, E30, E36, and E46), with one exception, place the CSB 30-100+mm forward of the E34. None of their rear halves will work without a bracket. The exception is the Z3, which has a very short rear half. Apparently all E34 use the forward of two CSB mounting holes, leaving a few cm of unibody bracket to work with. I don't have data to say whether the Z3's will fit on the same bracket, but it's possible.

Some 37BZ swap info for E46 states that the 37BZ is 106mm longer than the 310/320Z. This number is consistent (to within 1mm) with my measurements of the difference between A4S310R and 37BZ (115 +/- 3mm), and quoted differences between the 86mm and 80mm diff flanges (10mm), and between 525iM ZF driveshaft and the 525iA's (210mm), and between E46 330i/5 and 330i/6 driveshafts. Consistency after hours of researcheadache is relieving.

Further research, including two measurements I did firsthand and accurately (and one firsthand and not so accurately), shows that official driveshaft lengths are consistently ~30mm over both mine and Dorman's. There are a couple of discrepancies between all three, but that's the general pattern. So I guess official lengths includes the pilot tube, and Dorman's are reasonably reliable.

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. Singing6's comes to 1492mm but uses the 86mm CV; the extra 12mm perfectly explains the tight fit. The most reliable numbers have the 530iA shaft 8mm too short. The CV might be able to take that up, and using M3 giubo 26112226527 reduces the gap to 3mm, which it can definitely take up.

[Singing6]

Man, that is a lot of digging. It still sounds like there is no drop in driveshaft though?


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[moroza]

Edited my post above. I was mistaken about the 530iA being a drop-in, but it's within 8mm, or 3mm with an M3 giubo. That's close enough.

[Singing6]

Keep in mind a quote from the machine shop that did my driveshaft:

“we like to think that all the cars that are accident free have perfectly straight bodies but that is not the case. Stuff flexes. The driveshaft needs to be able to adjust. ⅛” is nothing in the world of driveshaft length”

After all the research you have done, we found my driveshaft is 12mm longer than it should be but it still fits and works fine. That is like ½”!

[wanganstyle]

deleted

[Onizukachan]

Really nice work by and to all involved.

[Singing6]

NO.

The modern 2019 method to convert a E46M3 SMG into a manual is to install an aftermarket shifter kit with self centering.
the SMG items simply unbolt and you are left with a manual transmission that can function with external self centering just as well as internal shifter centering.

moot point to pay or even bother to modify it to use internal centering

Quite a few companies make them and this avoids the issue of screwing with the gearbox entirely;
quite a few locally on the street and race track.

Great info, thanks for that. I had read that it took a bit of work and spare parts from a normal g420. I still like by ZF more though.


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