m50 conversion,running off m40 gearbox??

Post Thu Jul 26, 2007 12:48 pm

just a quick question, ive been told that I can use the m40 gearbox, prop and diff with a m50 conversion. is this true?

Post Thu Jul 26, 2007 12:58 pm

Well I know that a m50 gearbox will fit on a m42. ( driveshaft needed to be shortened) I also know that the 4 cyl getrags gearboxs are not that strong so even if it did bolt up it may not last.

I just cant tell you if a m40 and a m42 can share the same gearbox. If they do then the answer is yes.

B

Post Thu Jul 26, 2007 1:48 pm

if it does fit, what clutch and flywheel would I use with the m50 engine?

Post Thu Jul 26, 2007 1:59 pm

they supposedly do fit and good 4 200lbft..

Post Thu Jul 26, 2007 9:37 pm

kingwajuk wrote:if it does fit, what clutch and flywheel would I use with the m50 engine?

im using the m42 box with standard m50 clutch flywheel and starter motor. all fits up nice.

the m40 box is same dimensions as m42, and same dimensions as e34/e36 m50 boxes. (i have compaired side by side).

possibly a weaker box but alows standard e30 difs to be used as it dont fuck up final drive ratio.

m

Post Thu Jul 26, 2007 11:13 pm

if I used the m40 gearbox on a m50 engine would I have to use the e30 m40 prop also?

Post Fri Jul 27, 2007 1:17 am

kingwajuk wrote:if I used the m40 gearbox on a m50 engine would I have to use the e30 m40 prop also?

no, the prop would be too long as the m50 pushes the box back when you use the e36 mounting arms

an e30 m20b25 propshaft from a 325i would fit perfect ;)

Post Fri Jul 27, 2007 1:32 am

would i still use the original m40 gearbox mounts?

Post Fri Jul 27, 2007 6:25 pm

Ive been told the M40 box wouldnt fit an M50, but the M42 would.

AFAIK the M42 has a bigger bell housing so it will clear the M50 flywheel etc. When I say the bell housing is bigger, I mean its deeper where the flywheel/clutch would be.

If this info is wrong I will be well pi$$ed off, as I passed up an offer of a decent M50 because I only had the M40 box etc to convert my touring.

Post Fri Jul 27, 2007 6:39 pm

well ive heard of a m40 gbox being used on a m42 engine and if a m42 gbox fits a m50...then why can't a m40 gbox fit a m50 engine??

Post Fri Jul 27, 2007 6:52 pm

Because apparently the M42 bell housing is deeper than the M40 one, even though the bolt pattern maybe the same.
I was told the M40 bellhousing wouldnt fit over the M50 flywheel even without the clutch fitted, but because of the extra depth in the M42 bellhousing, that fits ok.

Like I said, I was told this and was shown an M42 box and M40 box side by side (or what I was told to be an M42 box), so I have no reason to doubt this. But I wont be happy if its duff info - my touring would of been M50'd ages ago otherwise.

Post Fri Jul 27, 2007 7:36 pm

Ive just done some research and it apears that if you use the m40 gbox on the m50 you would need to use the m20 clutch/flywheel...can anyone confirm this??

Maybe the m40 gbox wont fit with the m50 clutch/flywheel but will if you use the m20 combo??

Post Sat Jul 28, 2007 10:01 am

kingwajuk wrote:Ive just done some research and it apears that if you use the m40 gbox on the m50 you would need to use the m20 clutch/flywheel...can anyone confirm this??

Maybe the m40 gbox wont fit with the m50 clutch/flywheel but will if you use the m20 combo??

Thats possible I guess, but the M20 flywheel wont fit straight on to the M50. Some machining is needed for clearance, but its not too bad IIRC. Someone was going to try an M20 flywheel/clutch in an M40 box to see if it would work, but Im not sure anything came of it.