Gearbox choices ! so many......

[Rallyprep_UK]

Hi

My friend and I are both doing 24v conversions. Ben has a 2 door 316i manual and has a single vanos 2.5 engine kit from an e36.

I have a 2 door 325 manual and am fitting a single vanos 2.8 engine from an e36 328 sport.

We have researched the 24v conversion a lot and everything is fine and understood (sump/servo etc) except there seems to be so many options regarding gearbox choice.

I see the E30 318is gearbox is a common choice to use, does anybody know if the E36 318is gearbox is the same ? I am guessing the ratio might be different but hoping they are the same !

Bens car will be a road car and maybe the odd track day, but mine will be getting only serious track abuse and I was wondering if there is much difference in strength or drivability in the various gearboxes or they are all very similar ?

Ben has bought a 320 manual gearbox/flywheel/clutch/diff etc but I know another local guy who used his original 316i gearbox setup on the same engine conversion ?! Personally I would not want to run that power through a small case diff !.

The intention was to use m20 gearbox/diff etc or both cars. Are we doing the right thing ????

The 328 gearbox is still on my engine but im not sure what happens about diffs If I use that because I already have a 325 sport gearbox and lsd + lightweight flywheel. I also have access to e30/36 "is" gearboxes at the right price.

Any opinions would be much appreciated before we start bolting the wrong things together or wasting time lol.

Thanks
Will

[Rallyprep_UK]

with the IS box you can keep your 325i diff and prop shaft and it sits in the correct position for the box mount no bending linkages or hammering the transmission tunnel is needed for it fit either.

This seems to be the benefit of using the "is" box. Is this the only ones ? If so I would rather use the m20 sport setup.

[baptie0]

if you use the 328i gearbox you are going to need a diff, best to use the box, diff, prop you already have, just modify the gearbox mounting/selector rod.

[DanThe]

What ratio is your LSD? The 328 gearbox is a 1:1 5th gear, the E30 box's are overdrive 5th 0.83:1 so if you fit an E36 box and keep your E30 diff you are effectively loosing a gear and have reduced top speed.
Although, if you are only using the car on track a 3.64 diff and 328 gearbox isnt a bad choice as acceleration will be greatly improved

[Rallyprep_UK]

What ratio is your LSD? The 328 gearbox is a 1:1 5th gear, the E30 box's are overdrive 5th 0.83:1 so if you fit an E36 box and keep your E30 diff you are effectively loosing a gear and have reduced top speed.
Although, if you are only using the car on track a 3.64 diff and 328 gearbox isnt a bad choice as acceleration will be greatly improved

yes, that had crossed my mind ! I'm not actually sure what ratio my diff is ! cant remember off hand Will have to check...

[Rallyprep_UK]

ok I have found out something interesting !!!
(uh oh...)...

The E46 330d has a 6 speed manual box...
1st 5.08
2nd 2.80
3rd 1.78
4th 1.26
5th 1.00
6th 0.84

The 325i Sport gearbox i have has these ratio's (according to wikipedia...)

1st 3.76
2nd 2.33
3rd 1.61
4th 1.23
5th 1.00

I have the 330d gearbox and am going to offer it up to the m52 on tuesday so check back to see what I have learnt ! fingers crossed...

[DanThe]

Where did you get those ratios from? That is a VERY short 1st gear! more or less useless IMO unless you are using a diff ratio of around 2.5, even then by the time you get to 3rd/4th you wouldnt be going fast enough to pull properly

It will bolt up but you will still have a lot of work ahead of you to get everything to fit. Leave it in the diesel

[Rallyprep_UK]

good ol google...
http://forum.e46fanatics.com/showthread.php?t=715749

Yes I knew first would be useless unless you want to pull trees down, but I was more interested in the 0.84 of 6th.

It would be ideal for the long straights, while keeping the other gears short without compromising top end !.

I am not sure if the "1st gear ratio information" is right as I also find that very hard to believe so will also check that by turning the box over on monday...

[bss325i]

The 325i Sport gearbox i have has these ratio's (according to wikipedia...)

1st 3.76
2nd 2.33
3rd 1.61
4th 1.23
5th 1.00

Well thats wrong as a getrag 260 box doesn't have a direct drive fifth.

[Rallyprep_UK]

Well thats wrong as a getrag 260 box doesn't have a direct drive fifth.

Nothing wrong with a 260, I would just like a gearbox with less than 1090937092358693826896192miles on it thats all lol.

[DanThe]

Barry is saying the gear ratios you gave for the 325i sport box (Getrag 260) are wrong as 5th gear should be overdrive, not 1.00

Unless its some US mix up and is supposed to be an E36 box

Id just stick with the 328i box as its regarded the strongest out of the lot and is less likely to give problems.
If it turns out you have a 3.91 LSD then you would be better off with an iS box IMO

[Rallyprep_UK]

ok yeah I just read that again but properly haha !!!
wikipedia = FAIL

So if I am to use the 328 box, would it be worth putting the m20 flywheel in as IIRC the 328 one is dual mass (something else that can fail) and heavier ?

Its looking more and more like I will use the 328 box. And the bonus is that it's already attatched !!! I'm all for more strength and less effort...

[Dirty6]

Where did you get/what did you use to create a 2.93 LSD Will?

[DanThe]

328i sport used a 2.93 LSD

[Dirty6]

Strange as the 3.07 I have here from the E36, the crown wheel was set further toward the centre of the housing and wouldn't allow the LSD pack to fit between it and the casing.

[Rallyprep_UK]

I have used the M20 flywheel etc in my e36 328, makes a huge difference in the way it accelerates! You will need to use a taller thrust bearing or modify the clutch fork due to the lower profile of the clutch/flywheel assembly. I am using a 2.93 lsd diff in it to get the revs right for motorway use.

The diff wouldnt fit an e30 though right ?? Hope not because I sold it lol.

Doesnt a Bmw Z3M coupe have a 24v with an e30 type rear end ? I know the diff covers have cooling fins and fit the e30 diff so surely this diff will fit and be ideal for 24v swapping ?!

[Rallyprep_UK]

ps thanks for the flywheel info Will,

Will

[Rallyprep_UK]

ok thank you very much