m50 setup in e36 compact

[e30-EVN]

A mate of mine has a 316 compact and wants to run the same setup as I have in my e30-

I have an m50b25
M42 box ect

Can someone help with diff ratio ect, obv its going to be easier putting this into effectivly an e36 than it was into my e30 but there may be differences with this In that car.
Any help appreciated

Ant

[Kos]

is it an m42 e30 318is box ?

if so that in an e30 runs a 4.1 diff, you may want to look for a 3.91 lsd

when dan did mine, we used the m52 box and kept the OE compact diff which was a 3.38, i soon changed it to an e30 M3 medium case LSD with a 3.25 ratio.

also used the e36 prop, exhaust was custom made

[e30-EVN]

I'm running an m42 (e30) box in mine, will be running a 3.64 lsd.....

He hasn't sourced the gearbox yet, I'm just trying to get things straight beforehand.

So I get him an m50 from an e36 and an m42 (e36) box, the backends are effectivly e30 aren't they?....

So use his 316 prop ect is it mate?

Cheers so far

[Kos]

the prop needs to be matched to the box

if you were using the box that normally comes with an m50 then you'll need the prop too.

with the e36's M42 boxes i'm not sure if the gearing differs to the e30's.

the back end is effectively the same but you may need to hammer the floor pan 5mm to clear where the diff will foul it

[e30-EVN]

Ok, would an m50 be faster on an m42 box or the original m50 box? Obv it comes down to dif ratio aswel....

I'm thinking now then, m50 engine- m50 gearbox and m50 prop....

So we can use an e36 diff to make life easier at the back! Which ratio diff would you recommend mate?

I have a spare m20 fly ect which I will throw in for him to

[harry_p]

It depends what sort of diff you want, if you are ok with open diffs then there's the standard compact Ratios and the huge range of e30 ratios.

For LSD then you only have the e30 ones, I don't think they ever offered an LSD on compacts, and the normal e36 diffs won't fit.

The m50 box needs a low ratio diff to work and not scream it's head off at motorway cruising speeds, which pretty much limits you to e30 m3 If you want an lsd. Going with the m42 box like you have on your e30 then obviously the gearing is going to work out very similar to an e30 ams would work with higher ratio LSDs.

[e30-EVN]

Okay thanx for the info on that 1. Going with the m42 box will make diff choice easier I think then.

Just 1 more thing though, are the e30 and e36 m42 boxes different ratio's as kos suggests or are they the same just with different mouts?

Thanx

[leeparkes]

Not sure on early E36 M42 boxes but iirc early M50 E34's have an overdrive box (same as E30 ratio's)

Regarding the prop, my set up is 318ti box with an E36 325i prop,the 318ti prop was too long by about 50mm, you will also need to work out what gear linkage you will need.
Im running a 3.46 diff But im also running 18's with a 40 profile so have a larger rolling radius compared to say running 15's with a 50 profile.

Z3 diffs will fit too which are a low ratio

[Alpina99]

J*sus this is confusing !!
I asked some time ago & was told that the E30 M42 'box and the E36 M42 'box were the same and that I'd need a 3.64 diff for "general" running,
Is this now wrong ??

[Andyboy]

Not sure on early E36 M42 boxes but iirc early M50 E34's have an overdrive box (same as E30 ratio's)

You try and find one! I've only had two in 10 years.............

[DanThe]

Got one