E36 6 speed box?

[Mikey_Boy]

Hi Folks,

A quick question please - will the E36 M3 6 speed gearbox bolt up to the M52 - I am assuming it will as the bolt patterns should be the same?

If that's the case, will this box fit into the E30 shell with an M52? Looking at the gear ratios, I think this would be an awesome combo - surely someone has done this??

Cheers,
Mike

[DanThe]

Yes it will fit and work but the boxes are renowned for failing which pushes the prices up for decent ones being hunted down by E36 drivers

[Mikey_Boy]

Thanks Danthe - - so best to stick to a 'standard' 328 box then? Do you know how they fail??

Does anyone know the ratios of the 328 box?

Sorry - just feeding my curiosity!!

Cheers,
Mike

[xr666]

the 5th gear ratio is 1;1 on a 328 box & on the 6 speed box 5th is 1;1 & 6th is 0.83;1

[Mikey_Boy]

Thanks xr666 - I was comparing gear ratios and trying to work out what gear cluster and diff combo would make for a good trackday weapon without being too compromised for driving to and from the track - this led me to the use of the 6 speed box and maybe a 3.91 diff?

Having done some reading, I have noted that the 5 speed is considered stronger than the 6 speed, but just wondering what the failure of the 6 speed box is?

Cheers,
Mike

[DanThe]

The syncros wear out prematurely on the 6 speed Getrags, they jump out of gear and wont engage etc.

I wouldnt want one in a track car

328i

1 - 4.20
2 - 2.49
3 - 1.66
4 - 1.24
5 - 1.00

S50 6spd

1 - 4.23
2 - 2.51
3 - 1.67
4 - 1.23
5 - 1.00
6 - 0.83

[Mikey_Boy]

Thanks Dan!

Hmmm - premature syncho wear is pretty fundamental! Doesn't sound like the best solution for a trackday car...

I was comparing ratios compared to my 262 dogleg box and they looked pretty similar - as I am considering an M52 swap I was just considering gearbox options...

Thanks all!

[GeoffBob]

Mike,

I assume it’s the Getrag 420g to which you refer (as this is the one found on the E36 3.2 M3)

Appletree (Matt) has fitted a 6-speed Getrag 420g to his supercharged M42, see here

The Getrag 420g is extensively sought out down here and has been put to good use in a number of race cars. I am not aware of the synchro issues to which DanThe refers, but then I do not have sufficient experience with these particular boxes to confidently state otherwise. It is my experience, however, that any box sufficiently thrashed around the track will eventually eat its own synchroniser rings, and this is exactly the reason why my own gearbox has none.

SFAIK, the Getrag 420g has the ratios:
1st 4.32:1
2nd 2.54:1
3rd 1.62:1
4th 1.23:1
5th 1.00:1
6th 0.83:1

DanThe, is it possible that you are referring to the 6-Speed Getrag 560g or 217? If I am wrong I apologise, but I wouldn’t have thought the syncho’s on the Getrag 420g were any more likely to fail than on any other box (particularly the modern moly alloy rings), and I have seen the 420g put to good use on some very potent track-cars (FYI, see my project car thread Mike).

Mike, I am not sure how serious you are about this, or how much you are prepared to spend, but none, and I mean absolutely none of the Getrag boxes are track specific (and with good reason since they are employed on road cars). No matter how you work your final drive ratio you will always eliminate either your highest or lowest ratio gear while out on the track. The only proper solution is a set of track specific gears that typically start with a first gear ratio of around 2:1 to 2.5:1, and then progress upwards at intervals of typically no more than a 25% change in ratio, progressively decreasing down to around 12 to 15% from 5th to 6th gear.

[Mikey_Boy]

Thanks Geoff - spot on as always...

Just thrashing a few ideas around to be honest - my M20 / M52 / S50 deliberations continue! As you know from other threads and discussions, my fresh 262 gearbox has just been installed to the back of my M20 so I am still in the process of enjoying that on track and drift days!

I guess I am still hunting down that perfect BMW parts bin combo of road car that works on the road against track day warrior - whilst it would be easy just to buy a later car, I really want something E30 shaped...

Point of history though (which of course leads to the the points you make above) is that in the 80s, the touring car guys raced E30 M3's and Sierra Cosworths with road gearboxes, running just altered (shotpeened and tighter ratios compared to the road versions) ratios and full synchros - both Getrag boxes.. Also Porsche raced with a synchro box at Le Mans for many years - driver fatigue sited as the reason for this (4 speed as well such was the torque spread in the 917s...).

Thanks for the advice - great to see some really interesting projects out there raiding BMW parts bins!

[DanThe]

Not sure of the actual getrag number, just E36 evo 6 speed box's
Ive never dealt with one just what ive heard, also heard the clutch flexis sometimes expand under pressure which will help wear syncros

Braided clutch line FTW

[GeoffBob]

[Mikey_Boy]

Sounds to me as if you are keen to retain originality Mike, and that power is not your ultimate objective (and why should it be quite frankly). If you choose to retain and modify your M20 then I’d suggest keeping the Getrag 262.

Indeed Geoff - it's the conclusion I keep coming back to... The 262 box is really sweet!

I have no argument with synchronised gearboxes employed in motorsport Mike. A gearbox can be modified and swapped out, same as an engine can, and a professional team likely has the staff and budget to do so. For a race team the issue is one of ensuring the gearbox lasts the duration of the event. Us mere mortals, however, require our gearboxes to last longer, and that’s the crucial issue here.

Again absolutely right Geoff - Audi went to the (quite brilliant from a design point of view) lengths of realising their R8 boxes wouldn't last Le Mans so re-designed them to be changed in the pits in a few minutes and folded this into their race strategy. But of course, you are correct - we certainly don't have the luxury of frequent gearbox changes and I certainly don't have the desire to rebuild mine frequently!

Also, it is a well documented fact that an unsynchronised box shifts faster than a synchronised one, provided the driver is skilled at controlling rpm

Absolutely right - this problem was taken away from F1 drivers as you know by Ferrari when they introduced flappy paddles in 89.

As to the invention of the synchro box, there is some debate I believe - Porsche certainly perfected it, but the patent goes back to 1922 and I think it's Alvis who are credited with the first full synchromesh box back in the 30's...? I am no doubt opening a can of worms stating that!!

Porsche even went so far as to replace the differential on the 935 with a spool. That must have been a tough, albeit reliable, car to drive.

Indeed!! The 962 had a effectively a solid rear axle as well - no wonder those Le Mans guys are real heros!

Dan's point above about clutch engagement being a little compomised no doubt contributes to the problem with the E36 6 speeders...

Cheers,
Mike

[baptie0]

I have just purchased a six speed Getrag from an m3 evo for a bargain price, I hope its not been a mistake

[tim_s]

I think there's probably a lot of truth in the evo clutch lack of disengagement causing the premature box wear. When I test drove a few, I didn't really get on that well with the clutch - most of the clutches were biting with the pedal near at the floor and felt pretty tough, including the one eventually bought. I was sceptical about changing to a braided hose making any difference, but that was the consensus and sure enough changing it and the salve cylinder made quite a difference. I recall they have the same m/c, pedal etc but a larger dia. slave cylinder than the m52 cars, which possibly goes some way to explaining the pedal travel required. fwiw the evo's on 130k on the original 'box and it feels pretty good, the boxster's box is worse!