GEARBOX UPGRADE ??

[skidmark]

Hello, I am after some help/advice about which gearbox and what options are available for my BMW.

I would like to know what type of OE gearboxes will fit my E30 325i track day car. Do all BMW models of this era have the same bellhousing patterns/starter positioning/clutch slave mounting and are there 5 speed and 6 speed boxes with better ratio's available?I know of the 1:1 top gear dogleg sport/M3 box.
Are there any aftermarket dog box kits (non synchro) available or whole boxes?

I'm inclined to spend a bit of money on gear ratio's in the search for more speed rather than more horsepower (there's also a great deal of satisfaction in a gearbox full of really close ratio's). I have access to alternative diff ratio's, so can choose one to suit either direct top gear or overdrive or even underdriven I suppose.

Thanks for any ideas/advice you can add.
CHEERS
MARK

[M3GTR]

I think your best bet (unless you want to get into making your own bell housing) is the 325 sport box and then play with the diff ratio. You can fit an E30 m3 dogleg box, but you need to make up an adapter bell housing to do it. I know of a couple that were done in the Kumho series (I had one) but have rarely seen them elsewhere as it's totally DIY to do it. It was already fitted to the car I had though!

If you decide to go that way, I have a sport gearbox going on ebay soon unless I can get rid of it sooner! It comes with a free standard 325 box too!

[Simon13]

there is an M20 dogleg box these are very rare though and were fitted to certain 323's as an optional extra

this will bolt straight onto an 325i engine too

[northloop]

Hello, I am after some help/advice about which gearbox and what options are available for my BMW.

I would like to know what type of OE gearboxes will fit my E30 325i track day car. Do all BMW models of this era have the same bellhousing patterns/starter positioning/clutch slave mounting and are there 5 speed and 6 speed boxes with better ratio's available?I know of the 1:1 top gear dogleg sport/M3 box.
Are there any aftermarket dog box kits (non synchro) available or whole boxes?

I'm inclined to spend a bit of money on gear ratio's in the search for more speed rather than more horsepower (there's also a great deal of satisfaction in a gearbox full of really close ratio's). I have access to alternative diff ratio's, so can choose one to suit either direct top gear or overdrive or even underdriven I suppose.

Thanks for any ideas/advice you can add.
CHEERS
MARK

If you are trying to get better performance out of the car and your inclined to spend a few quid as you say, wouldn't you be better off taking the 325 lump out and replacing it with an engine and box from something with more grunt?

Playing about with gear ratios can give gains in some areas and loses in others. My current track car lunched its standard box and I replaced it with a shorter ratio version. Only because it was readily available. The end result is that acceleration FEELS better (whether it is or not I am not sure) HOWEVER the car now wont hold gears through sections it previously would. I am bouncing off the limiter and having to short shift to a higher gear.
I have since timed myself and found that both boxes give the same result, however I am stressing the car more with the low ratio box.

Just my thoughts on the subject .......

[ScottEgg]

Interesting comment Northloop, my Sport ate its box on Saturday at LLandow. The circuit has a complex which I was taking in second, holding it just below the red line for about 10 seconds every lap was a real killer for the car. I'm now looking for a replacement box and am considering my options but looks like another sport is likely.

[tomstickland]

If you lower the final drive you will improve the low speed performance, but lose out at the top.
This is because the higher ratio gives more torque multiplication, but the gears are "used up" more quickly.

I analysed this effect in detail with a numerical computer program a few years ago.

Personally I like lowered final drives, but it's important not to go too far with it unless you rarely reach top speed.

You can knock a few tenths of 0-60 or 1/4 mile times with a moderate increase in fdr.

[Simon13]

the 260 getrag box fitted to 325's in normal and sport mode were also fitted to E28+E34 535i's they can handle alot more power than a 2.5 can throw at it or even a high spec 2.7. They can take 260+bhp from the alpina/hartge converted 3.5's

[Andyboy]

The number (240, 245, 260 etc) is the torque capacity. But they are pretty tough and over engineered. To fit a 265 M3 box to an M20 you need a 1982 USA 528e bellhousing. Mega rare used, just about still available new.
The 245 323i box is a piece of rubbish, weak layshaft bearings. It wouldn't even be worth buying one for fifty quid. Best close ratio box is the E36 unit (bullet proof and about £50), I'm trying to think which one bolts to the back of the M20 AND sit at the correct angle?

[ScottEgg]

So am I right in saying that the E36 units can simply be swapped with my knackered E30 unit?, no adapter plates or nowt?
sounds great

[skidmark]

Thank you all for your input ........ this E36 box sounds interesting ......... I'm not too familiar with E36 model options ......... can you please advise which model/engine variant is the one to use ?

You say it is close ratio ........ does anyone have the ratio figures for this box so I can compare with my standard 325i figures ?

Will be interested in the answers to the above post ....... straight swap ?

Thanks for all the ideas.

[northloop]

Mark.

What exactly are you looking for? I have a feeling you are close to spending money on something you don't really need.

Your first post you said you are looking for more speed rather than more horsepower.

Where and for what are you using the car?

A low ratio box means you are going through the gears quicker and more often. Gear changes take time. It also means you are running the engine at higher revs for more of the time.

Way back when I started using cars on track I used to screw the nuts out of them and change gear here there and everywhere. After a bit of tuition I was taught to select a gear, hold it and drive through corners. Not only was it far more sympathetic on the engine, but I was quicker too.

If you're a racer and looking at rebuilds here there and everywhere then get the low ratio box, sacrifice some top end and enjoy. If you're looking for something for track days then dont.

That's my advice, but no doubt it will controversial with those keen to see you spend your money

[skidmark]

Hiya Northloop,

Thanks for your advice ........ not sure I agree with all of it and wonder if you are getting sidetracked by thinking I want a "low" ratio gearbox ....... you mention this twice in your post above ....... I am interested in a "close" ratio option.

I have plans for a fairly powerful 2.7 next year ....... the gearbox option I am looking for is aimed at this engine and will be used for circuit racing/trackdays, as well as two 7 day events, one an all tarmac stage rally event (700km of competition miles) and the other an all gravel (1000 km) event. Both these events are "down under".

Meanwhile my E30 with standard 325i (engine) that I am using for trackdays here is relatively pedestrian and would benefit from a box full of closer ratio's ........ this would of course have to have an appropriate diff ratio to complement it.

I have been fortunate to drive many cars with close ratio gearboxes and have never found one that I have felt would benefit from a wider set of gears. I know that some turbo cars (911's for instance) can be an exception to this, but equally I see very few race cars without a full compliment of cogs in the box all spaced very closely.

Interestingly, you seem to assume that because you have more gears that are spaced more closely, that you have to rev your engine harder ....... I find with close ratios that an engine feels free-er and more willing to climb onto the next gear such that changing gear earlier nets the same if not more speed than straining the revs to climb onto the next (higher/wider) ratio gear. (crikey, its not easy explaining this !).

I guess we are chasing the same thing but have different ways of going about it.

When you get your Ring car finished I would love to come over and have you impart some tuition on how to get an E30 around the most daunting track in this part of the world (or in the whole world ?). What lap time is your target at the ring ?

CHEERS
MARK

[northloop]

Hi Mark.

My current 205GTi with 130bhp and 864kg's has lapped in 8mins 45secs on sticky tyres. Obviously that is fwd

My old Subaru was quicker and awd

The E30 is another change this time to rwd. I thought it was about time for a change. With the standard engine I don't expect miracles, if I get under 9 mins I will be very happy, infact amazed Once the engine goes bang, which no doubt it will, we will put something a little wilder in. Hence the car is being built with a more powerful engine in mind for the future.

You are more than welcome to come over and have some fun. It might be worth you checking out the web site I help to run. It's www.northloop.co.uk and the forum linked to the front page will keep you interested for a fair while I especially recommend the project cars section and the 470bhp E30

With regard to the close ratrio box, I assume unless you have a very long final drive they will reduce your top end?

[HillclimbE30]

This mention of an E36 gearbox that fits onto a 2.5. Very interesting. I am wearing out a dogleg close ratio box (no overdrive, 5th is 1:1 ratio) in hillclimbs and will be needing a replacement or rebuild soon.

Does anyone know which one it is?
Do you have to modify bell housing?
Has anyone fitted one?