M20 flywheel on S50 / M50 / M52 swap.

[ste]

I'm just about to put the M20 flywheel onto the M52 crank (I don't want to use the heavy dual mass M52 flywheel). I've got a new uprated M20 325i clutch sat here waiting to go on before the 5 speed e36 M3 box is fitted and the whole lot can then be dropped into the shell.

I'm a bit confused though.

1) Do I use the M20 release bearing and M50 spigot bearing?
2) Do I need to use the M20 starter motor, and does this account for the lack of diameter compared to the M50 flywheel? Or, do I swap the ring gears on the flywheels and use the M52 starter?

Yep I could go and do some measuring but I'm putting off going into the garage as it's cold. All help appreciated!

[Brianmoooore]

I loose track of what bits I've tried with what sometimes, but I'm sure I've used an M20 flywheel, complete with starter motor on a M5X of some kind.
There's also a current thread on the US Yahoo E30 twincam group on the same subject, where someone has confirmed it.

[g57yle]

Im pritty sure the starters are the same. if i remember correctly i think i just used the m3 gearbox with its own bearing, if spigot bearing is the pilot bearing, you just use the one for that gearbox

[Brianmoooore]

Im pritty sure the starters are the same.

If I'm remembering correctly (This is a work in progress - hasn't been fitted to a car because of E39 sump - but has been cranked over on the starter motor), the 325 E30 starter does have to be used with the E30 flywheel.
US site comes to this conclusion as well.

[Sooty]

You've got to use the starter that came with the flywheel.
i.e. M20 flywheel = M20 starter.

It took me nearly an hour of careful scrutiny , but it's because of the slightly different diameters of the starter dog gears.

If it's any help, I've got a lightened M20 flywheel in an M52 eng / 328i box combination & it cranks over with no probs.

Iain S

[DanThe]

The ring gears are different, only slightly but I wouldnt risk running either or.

Im using all M20 parts, starter, flywheel, clutch and release bearing.

Will be doing some measuring up for the release bearing on my new engine though as my clutch pedal is starting to harden up quite a bit.

[ste]

Cheers fellas - I've been following the thread on the US Yahoo E30 twincam group too but I don't trust Americans to have much intelligence.

M20 everything it is. Engine in in the next few days. Can't wait.

[Brianmoooore]

but I don't trust Americans to have much intelligence.

Know what you mean, but there are a few on here, so I wasn't going to say so! Ian (Haynes) posts on there and points them in the right direction from time to time.

[ian332isport]

Engine in in the next few days. Can't wait.

Ste,

Give me a shout tomorrow if you need a hand

Ian.

[Andyboy]

Why are you using the 5 speed M3 gearbox? It's nothing special and is the same as the 328i box. The M20 325i box is the one to use. It has a good long overdrive fifth and is very strong, more than strong enough for an M52. It also bolts straight onto an M50 or M52. The M20 flywheel only fits an M50/52 after you've skimmed 4 or 5mm from the rear face. This is because the M52 sump has a couple of lugs for retaining bolts that foul the standard M20 flywheel. You CAN grind these lugs down until the flywheel fits but it's cheap enough to skim a flywheel. Make sure you go to a proper engine machine shop, not some twat with a lathe. Get it wrong and the engine will vibrate like a bastard anmd possibly fracture the crank.

With the M3/M52 box, you need the matching spigot bearing as the input shaft diameters are different.

So: M52. E30 325i gearbox, flywheel, clutch, release bearing and fork, starter motor and spigot bearing.

[DanThe]

My M50B25 engine is on the floor now with the gearbox off.

If you can wait I will be taking some measurements of the original clutch tomorow, unless your already a runner

Dont know about anyone else but I would rather use the gearbox that goes with the engine or at least one that is designed for the amount of tilt the engine has. Dont fancy those bent linkages and extra tilt on the thing

[m-dtech]

got any measurments of the length of m20 & m40 gearboxes ??

[ian332isport]

Why are you using the 5 speed M3 gearbox? It's nothing special and is the same as the 328i box. The M20 325i box is the one to use. It has a good long overdrive fifth and is very strong, more than strong enough for an M52. It also bolts straight onto an M50 or M52. The M20 flywheel only fits an M50/52 after you've skimmed 4 or 5mm from the rear face. This is because the M52 sump has a couple of lugs for retaining bolts that foul the standard M20 flywheel. You CAN grind these lugs down until the flywheel fits but it's cheap enough to skim a flywheel. Make sure you go to a proper engine machine shop, not some twat with a lathe. Get it wrong and the engine will vibrate like a bastard anmd possibly fracture the crank.

With the M3/M52 box, you need the matching spigot bearing as the input shaft diameters are different.

So: M52. E30 325i gearbox, flywheel, clutch, release bearing and fork, starter motor and spigot bearing.

I see what you're saying Andy, but you also have to deal with the angle change of the E30 325i box when bolted to the M50/52. This creates problems with the gearbox mounting and the gear linkage. Neither is a show stopper, but it just adds more work.

By the time you have modified the M20 flywheel, changed the spigot bearing, modified the gearbox mounting and gear linkage, you could have fitted the correct box in the first place. Okay, you now have to fit a different diff ratio to compensate for the lack of an over-driven 5th gear, but that is also a simple bolt on job. It just seems like a lot more work to me.

Ian.

[DanThe]

Extra 10° I think

[m-dtech]

how is that 10 degs going to affect the oil flow / levels in the box ?

[ian332isport]

how is that 10 degs going to affect the oil flow / levels in the box ?

Probably not much. There's plenty of people in the US that have used the E30 box without any reported failures that I'm aware of.

Ian.

[DanThe]

Would be like going round a roundabout constantly

[Andyboy]

Why are you using the 5 speed M3 gearbox? It's nothing special and is the same as the 328i box. The M20 325i box is the one to use. It has a good long overdrive fifth and is very strong, more than strong enough for an M52. It also bolts straight onto an M50 or M52. The M20 flywheel only fits an M50/52 after you've skimmed 4 or 5mm from the rear face. This is because the M52 sump has a couple of lugs for retaining bolts that foul the standard M20 flywheel. You CAN grind these lugs down until the flywheel fits but it's cheap enough to skim a flywheel. Make sure you go to a proper engine machine shop, not some twat with a lathe. Get it wrong and the engine will vibrate like a bastard anmd possibly fracture the crank.

With the M3/M52 box, you need the matching spigot bearing as the input shaft diameters are different.

So: M52. E30 325i gearbox, flywheel, clutch, release bearing and fork, starter motor and spigot bearing.

I see what you're saying Andy, but you also have to deal with the angle change of the E30 325i box when bolted to the M50/52. This creates problems with the gearbox mounting and the gear linkage. Neither is a show stopper, but it just adds more work.

By the time you have modified the M20 flywheel, changed the spigot bearing, modified the gearbox mounting and gear linkage, you could have fitted the correct box in the first place. Okay, you now have to fit a different diff ratio to compensate for the lack of an over-driven 5th gear, but that is also a simple bolt on job. It just seems like a lot more work to me.

Ian.

I thought the M50/52/54 engine could be mounted at the correct angle? I'm sure there are BMW engine mounts available to mount it at the same angle as the M20.

[ian332isport]

I thought the M50/52/54 engine could be mounted at the correct angle?

Correct angle for the M20 box, but surely not for the M50/52/54 ?

I'm sure there are BMW engine mounts available to mount it at the same angle as the M20.

I guess you may be able to do something with mismatched mounts, but the engine would be running at an odd angle (instead of the gearbox). Not sure if this would cause problems though. I guess it may make oil surge an issue if you tracked the car.

Ian.

[m-dtech]

could the engine mount not be altered to take into consideration the 10 degrees ?

would have to raise the front right mount and drop the left...

[DanThe]

M20 mounts bolt on no problem.
The problems start when you try to install the engine with them, sump is at an angle so your dipstick is now useless, could possibly cause oil pickup problems? The inlet manifold is now even closer to the servo, exhaust fabricating has also been made harder due to the gap between the block and column now being tighter.

I already tried it.

Those few degrees are very usefull you know

[m-dtech]

what issues are there with angles on the m40 box ?

[Brianmoooore]

Those few degrees are very useful you know

Which is presumably why BMW introduced them in the first place.

[m-dtech]

spiggot bearings are the same on the m50 & m20 according to ECP

[DanThe]

No they are different intenal diameters

M50

M20

[ste]

Why are you using the 5 speed M3 gearbox? It's nothing special and is the same as the 328i box. The M20 325i box is the one to use. It has a good long overdrive fifth and is very strong, more than strong enough for an M52. It also bolts straight onto an M50 or M52. The M20 flywheel only fits an M50/52 after you've skimmed 4 or 5mm from the rear face. This is because the M52 sump has a couple of lugs for retaining bolts that foul the standard M20 flywheel. You CAN grind these lugs down until the flywheel fits but it's cheap enough to skim a flywheel. Make sure you go to a proper engine machine shop, not some twat with a lathe. Get it wrong and the engine will vibrate like a bastard anmd possibly fracture the crank.

With the M3/M52 box, you need the matching spigot bearing as the input shaft diameters are different.

So: M52. E30 325i gearbox, flywheel, clutch, release bearing and fork, starter motor and spigot bearing.

I'm using the M3 box because as you say it's the right one for the engine. Using the M20 box introduces a list of headaches as already indicated. Botched gear linkage that feels awful or a tilted engine, useless dipstick, oil pickup issues causing starvation and even more problems with manifold fitment.

The M20 flywheel also fits straight on the M52 with no problems at all, or at least it did on mine.

[Andyboy]

I'm led to believe that using the 318i M40 gearbox leads to the gearchange being tits up and that the M20 box sits the right way up. I'll try and find out for definite.

Another way would be to sit the M52/M50 in the engine bay so it's sat properly. Then offer up an M40 318i box and see if it sits right. The little M40 (240) gearbox is very strong and will handle 200 bhp alright.

As ever, the box to look out for is the very early (H plate) 520i and 525i 24v. It was a regular Getrag 260 box with overdrive fifth but was designed to go with the M50 engine. I've been looking out for one in breakers but no joy yet.

[DanThe]

M20 box is at the wrong angle on an M50. Deffo

Are you sure about the overdrive Andy? I thought they just had the smaller output flanges

[Brianmoooore]

Change in 5th gear ratio would need a change in diff ratio to compensate, so a look at the diff on the ETK should show.

[ste]

The little M40 (240) gearbox is very strong and will handle 200 bhp alright.

That may be the problem...

[Andyboy]

Okay, so it's the M40 gearbox that fits then!
Years ago, a hero built a 2002 Turbo with Weber Marelli, a modified Garret from an Escort Cosworth, E30 318i head and manifold. It was all rebuilt and modded by AVA in Glasgow and the gearbox used was a standard Getrag 240 five speed from an E21 316 1800. This is the same unit as the M40 but in a slightly different casing. The M52 might have more than 200 bhp but it won't have anything like the torque of a blown 300 bhp M10. If you found a good low mileage unit (About £50) this should do the job. Eventually it might get noisy and the answer is another fifty quid and an afternoon's swearing!

According to Getrag, the 260 gearbox can handle up to 220 lbs ft torque but both Ant's 2.5 Turbo and Toby's 3.5 turbo both give a LOT more than this. If Toby's 260 hasn't shat it's gears out with all the grief he gives it (and 350-400 lb.ft?)....well, you know what I'm saying.
These old Getrag units came from an era when BMW's were overengineered - not like the box in my E36 320i where second and third are a bit notchy when cold and E36 M6 six speed units last about 11 minutes.

[jaistanley]

What diameter id the M20 clutch? I have an S50B32 engine and the M3 3.0 (5spd) gearbox and would like to loose the heavy flywheel too..

Will the clutch be up to the job?

Many thanks.

Jai

[dan_emaps]

i wouldn't see the point in changing to an e30 box tbh, i think the M3 5 speed box is a good unit, afterall i've seen plenty of 3.0 M3's on silly high mileage with the orignal box, so i wouldn't exactly call them weak. My 328i sport of course had this box and with a Rogue Engineering short shift it was an absolute pleasure to use, infact even though i sold my car on 88k, i didn't drive one other car during the time i had it with a gearbox that felt anywhere near as good.

[Jimbob]

So use an M40 gearbox instead of the M20? What flywheel will fit? And if using the M40 gearbox does it still mean a custom gearbox mount is required?

I'm lost

[Andyboy]

i wouldn't see the point in changing to an e30 box tbh, i think the M3 5 speed box is a good unit, afterall i've seen plenty of 3.0 M3's on silly high mileage with the orignal box, so i wouldn't exactly call them weak. My 328i sport of course had this box and with a Rogue Engineering short shift it was an absolute pleasure to use, infact even though i sold my car on 88k, i didn't drive one other car during the time i had it with a gearbox that felt anywhere near as good.

True - and I guess it keeps things simple. It all depends if you want to/can afford a 3.25 ratio M3 diff and that 328i/M3 box to start with. As far as I'm aware the 320i and clutch fits within the M40 box okay.