gearbox options

Mon Jul 07, 2014 5:42 pm

Having a m50 conversion in my 316 e30 in the up coming months and just wandering about my gearbox options, I know the e30 box will fit with the m50 but will it handle the torque? Also in theory would like the e36 box just because I like the fact that it originally came with the engine..but I know that the linkage will be at the incorrect angle... any fixes for this? What's peoples opinions?

I know I could use the search option but it's nice to actually have a conversation with someone that has some knowledge...

Mon Jul 07, 2014 6:37 pm

The gearbox and linkage is only at an angle if you use an E30 M20 gearbox on an M50/52 engine.

I'm currently smoking about in an M52 touring running the standard 318i M40 gearbox. The car has only been on the road for a month or so, but no problems so far. I would think it will be fine for road use, but as its a drift car, I'm not sure how it will last with the abuse - if/when the gearbox or diff gives up, we will change to an E36 box.

The E36 box will bolt straight in (no twisted linkage), but you will need to change your prop and find a diff with a more suitable ratio - somewhere around 2.93 to 3.25.
This is why some people opt to use the M20 gearbox and modify the linkage and gearbox mount to suit the new angle of the gearbox.

Mon Jul 07, 2014 6:49 pm

Thanks for the answer... the person doing the conversion for me also has a 325 tourer that he's breaking....would that be more of a suitable diff? I also have the prop off the e36 as well as the one off my e30...

Mon Jul 07, 2014 6:52 pm

Nope, no e30's bar the m3 had a direct drive box so everything is too short.

You can use an m3 diff, or build an e36 final drive ratio into an e30 diff casing

Mon Jul 07, 2014 6:53 pm

Ratio will still not be suitable for an e36 box but it will be a medium case which your 316 diff will not be.
If you keep the e30 box then use the touring diff.

Mon Jul 07, 2014 6:58 pm

So if I keep the e30 box on the tourer diff what do I do about the twisted gear linkage? Is it a case of modding the linkage arm?

Mon Jul 07, 2014 7:02 pm

Your 316i will have a small case diff, the 325i touring will have a medium case. The medium case diff will be more suitable in terms of strength, but the ratio will still be too short if you use the E36 gearbox, meaning high cruising revs and a pretty useless 1st gear.

If he's breaking the 325i, you could use your M40 box and prop, and the diff from the 325i. Or buy the 325i box, prop and diff from him and use those, but you will need to mod the gear linkage and gearbox mount.

Either way, you will want the 325i flywheel and starter from him, get it lightened and fit it to the M50.

Mon Jul 07, 2014 7:05 pm

Thanks mate...more things to think about a˜a

Tue Jul 08, 2014 7:38 pm

M40 box would be fine on the road, heavy drifting kills them tho, killed 4 in 2 years

Tue Jul 08, 2014 10:03 pm

That's lucky in have a spare a˜a

Tue Jul 08, 2014 10:16 pm

General concensus is the E36 328i box makes the better car - having only driven this variety, I can”˜t compare to an M52”˜d E30 with an E30 gearbox. The 328i ZF ”˜box is dead strong and has a slicker shift than an E36 box. Worth the effort perservering looking for a differential to match it to. Any diff from a 6-cylinder Z3 will fit the bill.

Thu Jul 10, 2014 12:46 pm

Is the z3 6 pot diff a straight fit then ?

Thu Jul 10, 2014 12:52 pm

You might need the output flanges from your old diff to match the driveshafts - but swapping them is a 10 minute job. Otherwise, yes, a straight fit.

Thu Jul 10, 2014 1:58 pm

Motorhole wrote:You might need the output flanges from your old diff to match the driveshafts - but swapping them is a 10 minute job. Otherwise, yes, a straight fit.

Careful..this guy's base car is a 316i touring,so will have a small case diff...

He needs a medium case diff,for the later direct drive 'box a diff around 2:90/3:25...with an ex M40 Getrag an E30 3:64/3:73..
So an ex Z3 diff will need the E30 medium case type flanges,the small case type will make the diff too wide.

Thu Jul 10, 2014 2:09 pm

daimlerman wrote: Careful..this guy's base car is a 316i touring,so will have a small case diff...

He needs a medium case diff,for the later direct drive 'box a diff around 2:90/3:25...with an ex M40 Getrag an E30 3:64/3:73..
So an ex Z3 diff will need the E30 medium case type flanges,the small case type will make the diff too wide.

Is that definitely the case with E30 small-case diff flanges? I have a Z3M diff in my car with small-case flanges from a 318ti, mated to 318ti driveshafts. They fit fine

Thu Jul 10, 2014 2:18 pm

Small case diff is narrower than the medium case,the difference for E30 fit is made by the flanges(oh er)small case has thick one's,medium case has thin one's.

Are compact driveshafts longer? Or shorter?

The OP could use Z3 diff,medium case flanges and E30 shafts for sure...

Bloody parts bin!

Tue Aug 26, 2014 10:52 pm

Sorry to hijack but I've got a 525i for a donor with an m50 in . Could I use the e34 gearbox ? Thanks

Tue Sep 02, 2014 9:20 pm

I have a E36 M3 6 speed on my M50... Just needed custom propshaft. Got a 3.91 diff too... MENTAL!

Tue Sep 02, 2014 9:34 pm

Flippin heck, a 3.91 diff with a 6 speed is mad!!

Do you use 1st gear?

My calculations make that doing 3200rpm at 70mph in 6th though so not too bad in the cruise.

I got the 3.25 diff which gives a laaaaazy 2450rpm at 70mph but am tempted to move up to 3.64 to make things a bit more interesting.