e36 gearbox swap question

[claude]

my car has 320i running gear with a m52b25 engine
can i fit a 6sp box? im asking because when you driving at around 65-75 mph the revs are quite high around 3.5k is this normal or would a 6 sp box help resolve this

thanks

[Gar]

A diff swap would be much easier and would change the rpm, 3.5k at 70mph seems a little high what diff is in it

[claude]

its standard gar
i cant remember exact rpm ut will note next time im out

[Valdelisbmw]

if its original 320i diff, so it should be 3.45 ratio
325i has 3.15 ratio , thats why revs so high
but with 3.15 ratio u might found it bit slow

[claude]

What about fitting new gearbox

[kdevitt]

What about fitting new gearbox

I might have the correct gearbox available soon if you want to hang on.

[claude]

No worries Ken let me know please

[Peter-E36]

I'd hang on to the diff and go for the 6 speed box Claudio, that will sort it.

Please trust me when I say 2.93 ratio will PISS YOU OFF... it's not worth a few rpms lower on the motorway.

Edit: Standard m52b25 (323i) and m52b28 (328i) diffs are 2.93:1 very, very long gears. The 3.15 out of the m50b25 (325i) or a 3.0 M3 diff might be a good compromise but I wouldn't bother to be honest. Large case 3.23 from an evo is a good option but You'll have to swap out too much for it to be worth it I'd say.

[claude]

so best option is to change box not diff? i really like lsd but which one if i do go for it,

[Peter-E36]

so best option is to change box not diff? i really like lsd but which one if i do go for it,

Yea a 6 speed with your current 3.45 ratio small case diff would be sweet

Otherwise if you want to go for an LSD, a medium case 3.15 would be a nice balance between motorway cruising and acceleration with the 5 speed box. Although I can imagine if you have the 3.45 ratio at the moment anything less will feel like a downgrade.

Edit: I seem to remember @[Valdelisbmw] having a rebuilt 3.15 LSD I was eyeing up last year. Not sure if he still has it but would be worth a shot as an alternative option