Z4M gearbox

[exdos]

I've just returned from a couple of days at The Ring in my Z4MC and my only real criticism of the car is the gearbox. I know that the shift from 1 <--> 2 is a bit stiff, but I can live with that because once you get to 2nd, you don't need to return to 1st again. The problem that I've had is on downshifting to 4th or 3rd gear: sometimes I just couldn't engage the gear I wanted before turning and ended up engaging an inappropriate gear to maintain power or even ended up coasting out of gear just to get round the corner. The car has done 28k miles and has been relatively lightly used for the past 3 or so years, and has possibly spent many of its miles on longer journeys with little gear changing. On the 500mile journey home, I tried to give the gear box as much use as possible, but it was still proving difficult at times to change down to 3rd and 4th. I have no problem in doing heel & toe with the car. It seems to be some mechanical resistance to the gear selection. Hhas anyone else experienced this problem and if so what is the solution?

 

[Z4M-2006]

I would have thought the synchro hub or baulk rings/springs were at fault.

Have you tried changing the oil to Amsoil MSF....Maybe worth a try?

 

[ga41]

Common complaint of Zpost members as well. I sometimes have trouble shifting from 3rd to 2nd. It's been reported that the stiffer Vibratech engine mounts alleviate this.

 

[daz05]

When mine was newer I had them put a new clutch in under warranty because of the 1st to 2nd issue and they said there were signs of corrosion I don't remember where exactly but after the box felt much better.

Another issue I've heard of is the clutch hydraulic fluid getting too hot and giving similar symptoms.

 

[exdos]

I would have thought the synchro hub or baulk rings/springs were at fault.

Have you tried changing the oil to Amsoil MSF....Maybe worth a try?

I've not done anything yet because I'd not found it such a problem until I really drove my car on track at 100% this last week.

The problem feels like some physical obstruction or resistance to engaging gear but I'm unfamiliar with the mechanics of gear boxes so your suggestion of synchro hub or baulk rings/springs sound like a lead to investigate. I want to take the car to a dealer and be able to discuss the problem knowledgeably so that I can get the correct solution. I appreciate the feedback and input of you guys.

 

[Beedub]

hmmmmm ive kinda had the same thing but it only ever happens when you in the extreme's.... i find coming into a corner, the cars loaded and you can get a denial or difficulty in shifting.... now... fast forward to my engine mount swap and this problem has been completely stopped dead.... im convinced the sloppy stock engine mounts are really causing alot of the shifting issues in the z4m, with the new mounts the drivetrain in general just feels soooo much better!! i actually really like the z4m gearbox and i find it a very nice positive shift ...

Definitely one of the best mods ive done to this car..... i can now full throttle 1st gear and the motor isnt bucking around too, the car just feels much tighter....

on taking off the stock mounts one was heavily compressed and the other seemed to be cracking from the heat... i also noticed with the new mounts the engine was sitting very slightly higher..... my car was literally pulling the stock mounts to pieces... Bear in mind they'd only done 10k miles...... the stock units are imo way to sloppy for this car.
The gearbox mounts are a great design however... i like them!!

and i STILL have yours btw.... i just need to find them im s**t... i know!!

 

[exdos]

Byron,

You've identified the same time this occurs as me there. It was happening when I was really on it and heel and toeing a downshift into a corner entry (which isn't normally a problem to me) and it also occurred on one 3 -> 4 upshift too, when I just couldn't find a gear. I can see how the engine mounts can be the cause of this because the transmission must be getting out of line when the engine is moving in 3D excessively and The Ring is a bumpy track too which will exacerbate any movement in engine mounts that might occur.

Please put your spectacles on 8) and get looking for my engine mounts but if you can't find them, on your recommendation I'll definitely get some.

 

[pilchardthecat]

I get the very very occasional crunch from 2nd to 3rd, but only when I'm >7000rpm in 2nd and i'm rushing the shift

Mine is a daily hack, so this could be another garage-queen ailment

 

[exdos]

Mine is a daily hack, so this could be another garage-queen ailment

The problem of having a few cars is that you can only drive one at a time. I treat my Z3MC and Z4MC like racehorses: they're very well looked after and want for nothing but when they're allowed out they're asked to gallop. 8) BTW I've received the honeycomb for the MAF mod today.

 

[Beedub]

Mine is a daily hack, so this could be another garage-queen ailment

The problem of having a few cars is that you can only drive one at a time. I treat my Z3MC and Z4MC like racehorses: they're very well looked after and want for nothing but when they're allowed out they're asked to gallop. 8) BTW I've received the honeycomb for the MAF mod today.

^^^^^^ Great way to put it

 

[carl]

Many years ago I did a track day in my Subaru Impreza and on the way home had problems changing from 4th to 5th. Dropped the gearbox oil and put Silkolene (Fuchs) SYN5 in and it was fine forever after (another 70k miles!)

 

[tertius]

I too had some gear shift issues, though in my case it was almost entirely fifth to fourth, e.g. downshifting after the crest at Schwedenkreuz, or at the top of Fuchsrohre. I suspect engine/gearbox mounts as well. My engine mounts are brand new but OEM. Not sure if there is a gearbox mount, though I assume there must be.

I found the solution was to take an extra fraction of a second over the shift and very positively select the gear.

 

[flimper]

Mine is a daily hack, so this could be another garage-queen ailment

The problem of having a few cars is that you can only drive one at a time. I treat my Z3MC and Z4MC like racehorses: they're very well looked after and want for nothing but when they're allowed out they're asked to gallop. 8) BTW I've received the honeycomb for the MAF mod today.

A racehorse will always need to be kept fit before it goes to the racecourse otherwise it will be very rusty for a couple of runs before finding top form

 

[exdos]

A racehorse will always need to be kept fit before it goes to the racecourse otherwise it will be very rusty for a couple of runs before finding top form

Correct, that's why I never SORN my cars and they go out for a gallop at regular intervals throughout the year. It also keeps the jockey in top form too. 8)

 

[mad4slalom]

this seem a common problem and i think is more the nature of the box than a mechanical problem as it does not happen all the time.in extreme track situations by afficianados of the ring such as exdos and beedub i think that engine and gearbox mounts may exagerate the problem and upgrading them would improve the symptons a lot. however in normal spirited road driving in which most of us limit the zeds to i have noticed the following,... when we drive a normal daily driver we are most of the time driving and gearchanging on auto pilot and muscle memory, ie, we change gear without even thinking about it. In the M, i have had on a few occasions the forth to third stiffness, baulk or denial, and also the coasting in the corner with no gear at all. I am convinced that this is just driver error, the m box needs a firm hand with directional pressure toward whichever gear you are selecting, if going back to my earlier point, you change gear on auto pilot and go for third from fourth not quite pro- actively enough you will get the stiffnes and denial, by the time you realise what you have done, the revs have dropped , you have to re select the gear , you loose rythym and smoothness . if you think about the gearchange be direct and positive , the box is a gem. the same with the no gear shift , you need to be on it thinking about which direction to apply pressure and be just firm enough. heel and toeing and just plain rev matching helps, i think just because you are actually thinking about the shift rather than driving on auto pilot. this is what BMW meant when they describe the M as a true drivers car. we want and love the man / machine interaction and the dynamic experience of these cars dont we ? if we wanted seamless shifts and a soul less drive we would have all bought honda's would'nt we. get out there, practise and enjoy, and remember you wont always be able to buy cars like these if the bean counters and the planet savers get their way.

 

[exdos]

I too had some gear shift issues, though in my case it was almost entirely fifth to fourth, e.g. downshifting after the crest at Schwedenkreuz, or at the top of Fuchsrohre. I suspect engine/gearbox mounts as well. My engine mounts are brand new but OEM. Not sure if there is a gearbox mount, though I assume there must be.

I found the solution was to take an extra fraction of a second over the shift and very positively select the gear.

I also had issues at Schwedenkreuz (5 > 4), the top of Fuchsrohre (5 > 4) and the turn at the end of Metzgefeld (5 > 3). All those corners are left-handers. It seems likely that the engine must pitch forward and to the right when this problem occurs.

 

[exdos]

this seem a common problem and i think is more the nature of the box than a mechanical problem as it does not happen all the time.in extreme track situations by afficianados of the ring such as exdos and beedub i think that engine and gearbox mounts may exagerate the problem and upgrading them would improve the symptons a lot. however in normal spirited road driving in which most of us limit the zeds to i have noticed the following,... when we drive a normal daily driver we are most of the time driving and gearchanging on auto pilot and muscle memory, ie, we change gear without even thinking about it. In the M, i have had on a few occasions the forth to third stiffness, baulk or denial, and also the coasting in the corner with no gear at all. I am convinced that this is just driver error, the m box needs a firm hand with directional pressure toward whichever gear you are selecting, if going back to my earlier point, you change gear on auto pilot and go for third from fourth not quite pro- actively enough you will get the stiffnes and denial, by the time you realise what you have done, the revs have dropped , you have to re select the gear , you loose rythym and smoothness . if you think about the gearchange be direct and positive , the box is a gem. the same with the no gear shift , you need to be on it thinking about which direction to apply pressure and be just firm enough. heel and toeing and just plain rev matching helps, i think just because you are actually thinking about the shift rather than driving on auto pilot. this is what BMW meant when they describe the M as a true drivers car. we want and love the man / machine interaction and the dynamic experience of these cars dont we ? if we wanted seamless shifts and a soul less drive we would have all bought honda's would'nt we. get out there, practise and enjoy, and remember you wont always be able to buy cars like these if the bean counters and the planet savers get their way.

I'm not sure what you mean by suggesting that there is a difference between "the nature of the box" and a "mechanical problem"? The gearbox should permit you to put the gear lever into the slot you select without difficulty, and if it doesn't, then there is something wrong with the design of the gearbox and its connection to the drive train: that's a mechanical problem. If the problem is corrected by fitting upgraded engine mounts then BMW should upgrade the mounts. If the problem is caused by parts fitted to the gearbox unit, itself, then those parts need redesigning. Sure, I want a strong gearbox that can handle the power from the S54 engine, but first I need to engage the correct gear(s), especially when flying around Schwedenkreuz or Fuchsrohre, otherwise the problem develops into a potentially lethal situation! It seems that most owners experience this problem at some stage, and we can't all be wrong. If the Z4M is a "true driver's car" as you say, then the car should be performing at its peak when at The Ring and the fact that it let me down on a number of occasions when the car was being used and driven like a true driver's car, means that the car is at fault. The fact that Tertius also suffered the same problem in his car at the same locations on the track as me, would suggest that this is a common fault with the Z4M.

I also drive a Citroen C2 VTS as a runabout (fantastic little car) and the 5-speed gear box is simple and it's so easy to find each gear, always. The best gearbox I've ever come across was on an Alfa Romeo 2.5 V6 24v I had some years ago: it was very close ratio box and so I found myself constantly skipping a gear up/down-shifting and it was never a problem engaging the correct gear. I don't see why BMW gearboxes can't be as easy to use as that Alfa one.

 

[BMWZ4MC]

I've been baulked on the occasional second-third upchange at maximum attack I suspect due to trying to change faster than the synchromesh can permit, but I've almost never had the problem you describe on downchanges even over many hundreds of track miles. I suspect the reason why my downchanges are reliable is because I always double declutch as well as rev-matching (even on the road). This obviates the need for the synchromesh to spin up and is most of use when entering a gear at over 7,000 rpm during aggressive downshifts into corners. I started double declutching in my first car (an ancient Fiesta) because the synchro was poor and the downchanges would frequently baulk (I used to drive it in the same way I drive my ///M ). Try double declutching when entering a lower gear at very high revs and you should find that the change is much smoother than with a traditional downchange.
The other thought I had is that your Mk I Exdos clutch stop may be preventing your clutch from fully disengaging - maybe this needs a tweak?
I've only had the problem you describe when downchanging when I've failed to coordinate hand and feet when tired at the end of a trackday.
Interestingly, the cast metal gear selector fork for third gear in my Audi TT suffered a fatigue fracture during a maximum rpm upshift leaving me with only third gear and no neutral. This made for an interesting drive to the garage

 

[mad4slalom]

its quite simple to my mind, its surely all about compromise, a full race car has solid gearbox and engine mounts so there is no movement that could compromise a shift , we couldnt live with those mounts on a road car so they make compromises so they are stiff enough to handle most situations but with a level of comfort thats acceptable. my point is that they are fine on the road once you realise how to change gear in a way that works best, but on the limits at the ring they are not up to it , . I wonder if a bmw test driver with hundreds of ring laps under his belt would experience the same issues on the same corners, maybe not i dont know, also show me a manual transmissioned race car that does'nt have a sequential box, this may be a reason for that too, so again it may be compromise over best options.

 

[Beedub]

i think if your using these cars , hell any road car past its remit your going to come up again things that need work, imo no biggy at all... like i say pound for pound.... the competition mounts added to my car have made one of the biggest and positive changes to my car.... i recommend them to anyone, stock or modded....
again i really like the feel of the z4m gearbox, im looking forward to doing a diff/gearbox oil change shortly to see if things improve..... i think i'll add a diff oil cooler as well this year....