Gearbox & rear diff

[na993]

Hope sifus can help:- how to tell what gearbox type we have ? ie is m20b20 & b25 same ratios ? i things theres coding/ part nos rite ? where is this located ?- the 325i sports came with shorter gearing g/box - wats the coding for this? ( this is not the dog leg version of the M3)- wats the std rear diff gearing for m20b25 - is it 3.75? how to tel wat the ratio - where is it written?- if you fit a 4.44, it will give better pick but crusing in 5th at @ 100kmh , wat the revs? anybody running tis ratio can share - is it very high - screaming?thnks

 

[na993]

.....anyone care to give opinion/ views??

 

[B33mEr]

I don't know whether this will help or not but here you go ...

http://www.metricmechanic.com/catalog/bmw-4-cylinder-transmissions-and-gear-charts.php

 

[Lionel_Koh]

Hope sifus can help:

- how to tell what gearbox type we have ? ie is m20b20 & b25 same ratios ?
i things theres coding/ part nos rite ? where is this located ?

-Yes its same ....

- the 325i sports came with shorter gearing g/box - wats the coding for this?
( this is not the dog leg version of the M3)

-Which 325 u refer to ?? E30 or E36?

- wats the std rear diff gearing for m20b25 - is it 3.75? how to tel wat the ratio - where is it written?

-Yes ...its 3.75...U can found it at d axle cover ...written on metal plate ...

- if you fit a 4.44, it will give better pick but crusing in 5th at @ 100kmh , wat the revs? anybody running tis ratio can share - is it very high - screaming?

-Simple ...by raising d rear axle ratio 10% ...u getting 10% more on ur rpm .....better pick up for sure but u also lossing 10% on ur top speed....

thnks

 

[loafer]

Hope sifus can help:

- how to tell what gearbox type we have ? ie is m20b20 & b25 same ratios ?
i things theres coding/ part nos rite ? where is this located ?

- the 325i sports came with shorter gearing g/box - wats the coding for this?
( this is not the dog leg version of the M3)

- wats the std rear diff gearing for m20b25 - is it 3.75? how to tel wat the ratio - where is it written?

- if you fit a 4.44, it will give better pick but crusing in 5th at @ 100kmh , wat the revs? anybody running tis ratio can share - is it very high - screaming?

thnks

Sometimes all it really needs is a quick google search. I'm just amazed how lazy some people are these days.

Anyway here is some of the info you're looking for, found via google.com.

http://e30world.com/specifications/BMW-E30-specs-table

http://en.wikipedia.org/wiki/BMW_E30

cheers.

 

[Lionel_Koh]

Sometimes all it really needs is a quick google search. I'm just amazed how lazy some people are these days.

Anyway here is some of the info you're looking for, found via google.com.

http://e30world.com/specifications/BMW-E30-specs-table

http://en.wikipedia.org/wiki/BMW_E30

cheers.

thanks 4 d infors ....seem i make few mistake there......

cheers

 

[june_yap]

Hope sifus can help:

- how to tell what gearbox type we have ? ie is m20b20 & b25 same ratios ?
i things theres coding/ part nos rite ? where is this located ?

- the 325i sports came with shorter gearing g/box - wats the coding for this?
( this is not the dog leg version of the M3)

- wats the std rear diff gearing for m20b25 - is it 3.75? how to tel wat the ratio - where is it written?

- if you fit a 4.44, it will give better pick but crusing in 5th at @ 100kmh , wat the revs? anybody running tis ratio can share - is it very high - screaming?

thnks

i was using 4.44 ratio in my M20B25 manual before....
pick up - fantastic
top end - 230km/h , but high rpm

what engine in your car? manual or auto?

 

[na993]

? - anyone care to translate the above ??

Bro loafer, thanks for the links :top: and am sure other would appreciate the info also, wonder if we can have some place where such info can be kept for reference by all - admin/ moderators ?
- i did search ( mybe not hard enuf) but couldn't get the info i needed, oddly the m20b20 is not reffered to, is it only for south east asia ?
The 325i Sports i reffered to, is e30, i believe they launched this to slot between the std 325i & M3, sport springs, std mtech bodykit, seat & steering, lsd and also the unique g/box with direct 5 gear - i believe the norm is o/dive 5th gear. Please correct me if am wrong.....

Thnaks also to others ... bro june - 230km, wat was the rpm ?mine a manual, as the car is work in progress, rojak g/box & rear diff, am trying to get it sorted out...

 

[loafer]

? - anyone care to translate the above ??

Bro loafer, thanks for the links :top: and am sure other would appreciate the info also, wonder if we can have some place where such info can be kept for reference by all - admin/ moderators ?
- i did search ( mybe not hard enuf) but couldn't get the info i needed, oddly the m20b20 is not reffered to, is it only for south east asia ?
The 325i Sports i reffered to, is e30, i believe they launched this to slot between the std 325i & M3, sport springs, std mtech bodykit, seat & steering, lsd and also the unique g/box with direct 5 gear - i believe the norm is o/dive 5th gear. Please correct me if am wrong.....

Thnaks also to others ... bro june - 230km, wat was the rpm ?mine a manual, as the car is work in progress, rojak g/box & rear diff, am trying to get it sorted out...

It's not easy to try to consolidate data from the internet. There is just too much and I don't think anybody would have the time nor energy to do it.

Here's an excerpt from Wikipedia regarding the 325iS.

Later when it became clear that South Africa would not be getting the M3, the 325iS was created. Initially this was merely a 325i 2-door fitted with a bodykit and a close-ratio gearbox (improving acceleration at the expense of top speed and economy, but more changes were made to keep the car competitive in South African saloon car racing.

Actually from reading your post I'm not too sure what you're really looking for. Are you trying to rebuild your E30 to exactly the same specs as the 325iS?

You're currently using M20B20?

Is this the information on M20B20 you're looking for? http://www.carfolio.com/specifications/models/car/?car=30943

 

[na993]

mines m20b25, g/box not sure & not sure wats the rear diff ( the plate tade). I'm not getting the feel of the 2.5, as the pull is not there so i suspect its the gearing. ( tuning ??)
My mileometer is accurate - comparing against Km marker on the higway but my speedo is over reading - shows 120km when speed is actually @ 100km. This are not critical issue ..
so am thinking perhaps to just change the rear diff to give better pickup.
tapi thinking kalu nak tukar r/diff,alang2 cari yg LSD, but i guess to find this is like needle in haystack :love:
tks for your assist though...to add to the confusion - latest possibility is that my g/box could be from a 323 ???

 

[loafer]

Maybe this can help you to determine what your rear diff ratio is.

http://www.5speedtransmissions.com/determine_gear_ratio.html

As for gearbox I think the only way to find out is to get the part number. Not so sure where the part number is so you'll need to find some E30 sifu to help you out with that.

cheers.

 

[fabianyee]

E30 320i is using the manual Getrag 240 gearbox while the 325i uses the Getrag 260. In terms of gearing, there's only slight difference for 3rd gear.

As for rear diff, 3.73 would be the optimal ratio for balance of pick-up and cruising speed. I've used the 3.73 on my M42 before, cruising speed at 3000rpm is about 120kph on the speedometer.

 

[na993]

tks loafer & fabian...yes still looking for the g/box part nos also...

recently, used penchala link & near Fed H/way exit the speed sign board showed 65kmh, but my speedo showing 80kmh - somuch diff, wat could be causing this ???:stupid:

but my mileage reading is accurate ???

 

[fabianyee]

tks loafer & fabian...yes still looking for the g/box part nos also...

recently, used penchala link & near Fed H/way exit the speed sign board showed 65kmh, but my speedo showing 80kmh - somuch diff, wat could be causing this ???:stupid:

but my mileage reading is accurate ???

What tyre size are you using???
The correct tyre sizes for E30:
1) 14" is 195/65/14
2) 15" is 195/60/15 and 205/55/15
3) 16" is 205/50/16

 

[na993]

205/50/ 16 ... but corectme if i'm wrong, speedo needle is electronic rite , so its picking reading from something else...
also i have read somehere the tire should be 215/ 50 / 16 ??

 

[fabianyee]

The signal comes from the rear diff..
I'm using 195/60/15.. speed difference is only 5kph according to my GPS....

 

[cempaka]

Gearbox part number

Wouldn't really matter if you had 240 or 260 though as the ratios are similar.

Changing the diff may help acceleration depending on what your mystery diff is, might as well get an LSD while you're at it.

Another possibility for lack of pickup is that your M20 is simply worn out. Have you done a compression test?

 

[loafer]

tks loafer & fabian...yes still looking for the g/box part nos also...

recently, used penchala link & near Fed H/way exit the speed sign board showed 65kmh, but my speedo showing 80kmh - somuch diff, wat could be causing this ???:stupid:

but my mileage reading is accurate ???

Heh don't trust that sign board. It always shows a different speed.

The best way would be to use a GPS and get your speed off it.

The electronics on your car is programmed for stock factory setup so I don't think it'll know to automatically adjust itself when you change your rims to a different size etc.

Try this form to calculate the difference in speed if you've changed your rims.

http://home.netcom.com/~sgalaba/tiresize.htm

 

[na993]

thanks for all the advice & suggestions, cempaka...yes LSD , know where i can get my hands on one ??

speedo reading, where is the sensor picking up the signal from ? rear diff ? gear box ?

assuming my tires wrong size, so am over reading - howcome my mileage reading is accurate?? it should be overeading also rite?

 

[fabianyee]

thanks for all the advice & suggestions, cempaka...yes LSD , know where i can get my hands on one ??

speedo reading, where is the sensor picking up the signal from ? rear diff ? gear box ?

assuming my tires wrong size, so am over reading - howcome my mileage reading is accurate?? it should be overeading also rite?

The speed sensor is at the rear diff, speed is the same no matter what ratio you are using...