E30 LSD Ratio Question

[darrencnz 10]

Hey guys

Currently having my LSD rebuilt with new bearings and seals. I called to find out the ratio as the tag was missing and could've been wrong anyway... Apparantely it's a 2.9

It's going in my 1990 E30 with 2.8L M52 which is currently running the standard Getrag 240 gearbox and im not exactly sure of the ratio of the current diff but its quite low. I cant measure the RPM as my tacho doesn't work at the moment but i hardly use 1st and she revs quite high in 5th on the motorway.

My questions are.....

1) What is 1:1 in the Getrag 240? is it 4th gear?

2) Does anyone else run this high ratio diff with this setup adn what are your thoughts?

3) When i eventually put a ZF 5spd gearbox, how will this change things?

I'm staying with the 2.9 regardless as it's being rebuilt now anyway, it was difficult to find in the first place and i got a sweet deal on it. Im just curious as to the difference between what im currently running as it seems like the polar opposite and i would prefer a higher final drive ratio than i currently have just not sure if this is too far in the other direction.

Chur

Darren

[polley 916]

yeah in the 240 1:1 is 4th gear.

with a 2.9 youll have quite long legs.

not sure what your car will have originally, if it was a 320 or 318 auto it prob has something around a 4.45 which will make it rev quite high.

I have a 3.64 with a 240 and its about right for me.

Edited May 15, 2015 by polley

[darrencnz 10]

yeah in the 240 1:1 is 4th gear.

with a 2.9 youll have quite long legs.

not sure what your car will have originally, if it was a 320 or 318 auto it prob has something around a 4.45 which will make it rev quite high.

I have a 3.64 with a 240 and its about right for me.

Are you also running the M52B28?

Mine was a 320SE NZ new 5spd from factory but i've replaced the current diff so i know it's not the factory one and didn't take much notice of the ratio, there was no tag on that one either.

I guess i'll just have to wait and see but currently 1st gear is almost useless, and im mostly curious about the relationship with the newer 5spd gearboxes as that's what will eventually go in there.

I can deal with longer legs with the 240 but if it meant even longer again with one of the newer 5 speeds i'd be a bit bummed. I just didn't expect it to be so high TBH

Edited May 15, 2015 by darrencnz

[westy 614]

If you do have a 2.9 or there abouts it'll be pretty much spot on with the ZF box if it's the E36/46 box with 1:1 5th. Close as damn it to factory 2.98:1.

[darrencnz 10]

If you do have a 2.9 or there abouts it'll be pretty much spot on with the ZF box if it's the E36/46 box with 1:1 5th. Close as damn it to factory 2.98:1.

Awesome... This is what i'm working toward so that's great to hear...

My Getrag 240 has done 250,000kms so it's geting replaced when i have some spare cash and can find a ZF 5spd

[CamB 48]

I agree with Westy - sounds like a great excuse to upgrade to a box with a 1:1 top. (edit - too slow, sounds like you are going that way, good call)

yeah in the 240 1:1 is 4th gear.

with a 2.9 youll have quite long legs.

not sure what your car will have originally, if it was a 320 or 318 auto it prob has something around a 4.45 which will make it rev quite high.

I have a 3.64 with a 240 and its about right for me.

So do you have a 240 behind the turbo? How does it enjoy that?

Edited May 15, 2015 by CamB

[polley 916]

I agree with Westy - sounds like a great excuse to upgrade to a box with a 1:1 top. (edit - too slow, sounds like you are going that way, good call)

 

 

 

So do you have a 240 behind the turbo? How does it enjoy that?

 

Yeah. Hasn't broken it - yet.