Auto to Man conversion on M50 or complete M30b35 engine and trans swap.

[OMP]

Hi there.
Maybe you have read the other thread about some issues that I have on the Auto tranny.

And, like I posted, unless a service does clear things up and car goes fine again, I am thinking about more long term solutions.
Here are my ideas:
Conversion from Auto to man. This would be my first bet, although we would need numerous parts for it, although here in Spain there are plenty of used parts cars and junyards with many E34s.
Good thing about this conversion is that I do certainly know that the M50 engine is 100% solid. No oil consumption, no nothing. It was basically rebuilt when I bought the car to the mechanic himself ( the same who is maintaining it) and I have had no issue, except for water pump and a few belts. But it runs good, good start, cold or hot.....

The other idea is to find a donor 535 ( manual) and put it in my Touring. I think the job would be much easier, but drawback here is that I wouldn't know how exactly how mechanically sound the engine and trans would be......
Good thing on these is that these type of engines/trans are rather cheap, so the initial purchasing price would not be the most important issue.

But then comes the compromise, as the 535, unless I find it from someone known, I would had to go thru the mechanics, and my M50 is in top shape, everything: Cooling system, engine insides, etc.

But I have a big doubt on the rear end. My car has the longest rear end ( except diesel models), that was available ( I think). It has a 2.64 and combined today with the auto box, is rather uncomfortable to drive, as 5th is way too long and gears are engaged too low in E and I do most of my driving in "S" mode.

And just to do a quick summary on my car, originally it's a 520i Auto imported from Germany in 95 and then swapped to 525 M50 non vanos, keeping the original 520i trans and rear end.
Since the mechanic did liked a lot this car, he did installed some goodies to it. It has E32 750i front rotors and 4 piston brake calipers, Bilstein B6 with original coils, E34 M5 complete exhaust, E36 Cruise Control system, electric, heatable sports seats, original Business with CD changer radio, M steering wheel, and interior is perfect except for some dirver's seat tears.

Anyway, and here is the key question.....Auto to man conversion keeping my known M50 engine or full ( engine + trans at same time) from an unknown M30b35?
Knowing that I suspect a huge change in terms of driveability even keeping my M50 with the man trans, is there much difference between the M30 and M50?

Thanks all for reading and giving ideas....

[moroza]

The M30 makes more power and at a lower RPM, with a very flat torque curve; I upshifted mine at 1500rpm in normal driving. M50 makes less and likes to be spun higher, feeling a bit lazy at lower speed. Big surprise there - 3.4 vs 2.5. The M30 has one of my favorite engine songs ever (it inspired my signature tachometer), while to my ears the M50 has all the musical charm of a vacuum cleaner. It drinks less, though; I averaged ~13L/100km in a 535i manual sedan, and currently get ~11-12 in a 525i automatic wagon.

Choosing between the two, I'd go with the one that's known to be good and already exists. The youngest M30 is 26 years old at this point, and so is its transmission. I'd say keep the M50 and change the trans and maybe the diff. What transmission is in it now?

From what I've seen, 2.65 is the lowest BMW diff except a 2.28 and 2.35, both Kompakt. I want a 2.28K in my car but not prepared for that kind of machine work. 2.65 was available in 210mm (850i) and 188mm (E34 525tds and others). Maybe there was a 168mm 2.65, I don't know. That's a tall ratio for a petrol E34, and I thought only the diesels got them. I had one in my previous car, but that had an M62B44.

[whiskychaser]

No disrespect but are you sure that diff ratio is 2.64 and not 3.64? That is the spec for the Euro 520. The 525i is 3.46. I think the 520i has the small case diff so that could be the reason the mechanic didn't change it

[fo3]

The m30b35 only makes ~15kW more than the m50. It is very strong though with nice torque due to capacity and has only a 9:1 compression so it suits turbocharging.
I'd only look at getting one if expecting a rebuild (as pointed out - they are all very old) and thinking about boost because they do very well there. In stock old tired form they are only good for turning money into co via the exhaust.

On the other hand you could keep a m50NV and look into stroking in the future, and boost because you have NV block and rods. There's an upgrade path for it (even if you don't take it yourself now or even later - for a future owner it has more potential). E34 535s are so common like why would you turn a m50 car into a m30? Keep an eye out for a manual 535 and buy that to drive and compare. I'd rather v8 swap into a m50 car than do a sideways swap to a m30 when it's so easy to just buy a factory version.

[ross1]

2.64:1?? In the heavier touring with 2 wheezing liters AND an automatic, can't be. Assuming this a typo and it is 3.46.
Auto box M50 cars in the US got 4.10:1 (which is usually regarded as too short for use with the manual gearbox) and they are still pigs off the line.
I am a big M30 fan but wouldn't bother with the driveline swap. It will be a lot of work and expense for little reward and lots more fuel. If you really want M30 power buy an M30 car.
The M50 is a bit lacking in low revs but that can be corrected with a bit lower final drive which will keep it in it's somewhat narrow power band, 3.64 seems ideal or even 3.91 would still be tolerable on highway.

[OMP]

Hi guys. You are absolutely right. I might just forgotten the exact figure, but you are right about the 3.46.
In this case, for me, it is way too long in terms of driveability. At normal, typical highway speed, which is 130 KpH, I am turning at about 2700-2800 which is too low for this car. In fact, any uphill will make me put 4th as the engine will turn at 4000 at 130 KpH, which is very reasonable in terms of putting power and torque on the ground. Over here people look desperately for short ratio diffs. A 4.11 diff might cost more than an entire car with another diff....
I don't know about spanish versions though. In the 80's mainly, Germany having their autobahns, ratios were very long to keep consumprion low, but in Spain, we still had lots of 2 way motorways. Nowadays this has changed dramatically and there are highways everywhere, although uphills and downhilss are still there.

I have been reading on the comments above and I can make myself a good idea about how the M30 and M50 drive around. What I would be afraid of is that the M50 might be hard to drive at low speeds before getting to thos 4000 rpms....
So, how about chipping the M50? Is there a possibility that a chip might do the ( little) trick?

Thanks and I am sure still reading you guys.

Regards

[moroza]

A chip won't help you much, but there are a few options for upgrading. Perhaps an S50B32?

Personally, I like tall gearing. It works well if you consider the top gear to be only for cruising, and simply accept that you'll need to downshift to pass. I find most BMW gearing too short.