what gearbox do i use

[terrybmw]

Hi all I am currently collecting the parts needed for a m50 conversion I have a m50 from a e36.I have already got the sump and pickup and dipstick,a modified exuast.I have a 318is lump in at the mo.what gearbox do I go for I have the m50 box that I'm told had a,new clutch.my car had the m42 box already I'm just confused as to which one I go for and what is involved I'm fitting each one.I am on a very limited budget so I don't realtime want to buy any more bits I just wana use what I got already.please help

[Brianmoooore]

Depends largely on what diff. you can get.
You say you have an iS engine at the moment, so the diff. you have at the moment is likely to be small case and have a fairly high (numerically) ratio.
The small case diff. isn't really up to M50 use, and your existing ratio, while tolerable using a M42 box, although too high numerically to be ideal, will be totally unsuitable for use with the E36 box.
You'll need something like a 3.64 or 3.76 for use with the M42, and something around 2.95 or 3.15 with the E36 box.

[terrybmw]

I'm using a 3.9 LSD at the moment if that helps(medium case that I fitted last month)

[RichIS]

im running m42 box and 3.91 lsd at the moment and if want to be fast thru the gears its the one for you just hope dont mind the noise on motorways as it revs quite high

[Jimbob]

That'll be no use with the E36 box, but would be fine with the M42 box. As Brian said if you want to use the E36 box a diff with a ratio from 2.93 to about 3.25 should see you right, these can be difficult to get hold of though..
You can utilise your current diff if you buy the CWP with any of these ratios, which are available from the States:
http://www.ebay.com/itm/BMW-DIFFERENTIA ... 3f12e2cf1c

If you use the M42 box you will need to get an M20 flywheel, M20 clutch, 320i gear linkages and 325i propshaft.
If you use the E36 box you will need to change the propshaft and possibly the gear linkages but I'm unsure of what you'll need.

I was playing with gear ratios yesterday and noted there was only a difference of 350rpm at 70mph using a 3.64 and 4.10 diff. I say only as it won't be a daily driver for me so it's not much of an issue.

[terrybmw]

Will the m50 flywheel clutch and starter not fit in the m42 box then

[E30BeemerLad]

they probably would, but you's be mad not to fit the M20 flywheel, clutch & starter as the flywheel is not a dual mass jobbie and is therefore much lighter, so the engine revs more freely

[DanThe]

That'll be no use with the E36 box, but would be fine with the M42 box. As Brian said if you want to use the E36 box a diff with a ratio from 2.93 to about 3.25 should see you right, these can be difficult to get hold of though..
You can utilise your current diff if you buy the CWP with any of these ratios, which are available from the States:
http://www.ebay.com/itm/BMW-DIFFERENTIA ... 3f12e2cf1c

Works out about £110 inc post + customs and handling fee when it lands here. Mental when there is a nice 3.15 diff in the for sale section for £150 that you just swap your slipper unit into and away you go

I always recommend using the E36 ZF box, much better than the earlier getrag scrap
As Lee says, M20 flywheel/clutch/starter FTW

[Jimbob]

Forgot you had one for sale mate

[DanThe]

Works out cheaper anyway, to change the crownwheel and pinion it means rebuilding with collapsible washers which is a specialist job

[terrybmw]

Thanks for the,info I think I'm gona go with my m42 box with a m20 fly wheel as I have these already.my next question is,what clutch do I use,the one on my m50 is brand new can I use this with the m20 flywheel.and what bearing do I use.as I'm a tight Bugger I don't realy wana spend to much more

[terrybmw]

I just read somewhere that the clutch's r different so I will need a m20 clutch.am I right in thinking I need to modifie the m20 flywheel to fit

[E30BeemerLad]

You can fit the M20 flywheel without modifying it, but you then have to shave a bit of metal off the fins at the very rear of the sump otherwise the flywheel gets crushed against the fins on the rear bowl of the sump and it won't turn over.

Usually, people either shave the sump (which is what I did) or use this opportunity to have a bit of meat taken off the rear of the flywheel, which makes an already lighter flywheel (than the M50/52 one) lighter still and makes the engine a real rev merchant.

24v lumps love to scream

[terrybmw]

Thanks I will have a look at the sump tonight

[Brianmoooore]

Clutch plates are indeed different. The M20 version has the shock absorbing springs built into the centre section of the plate, but the M52 just uses a plain disc with friction material on the outside and splines in the middle. The shock absorbing spring is part of the dual mass flywheel.

[deanocool]

hi dude. prob a bit late but i used a 318 e36 box (m44 i believe) with my m50 conversion. you will need a 3.08 diff if you like it slightly happy or a 2.93 if you want it spot on. i wouldnt bother with a 3.64 diff - you will have no 1st gear and seriously need a 6th as i found out lol. with the original 4.10 on i had no 1st or 2nd! the box i used also went straight onto the 320i prop that was already in aswell. hope this helps. standard 320i clutch, fly and starter and grind a small section away for the fly to clear - either that or have the fly lightened to make clearance. dont forget to use the correct slave with the box, some are too short and you will pop the slave pin out!

[DanThe]

Lightened FTW



Give me a shout if you want one doing

[terrybmw]

That looks good I want one