[JamesUKE92]

Hi all,

SYNOPSIS:
----------
I have an experiment for other 6MT owners with crap gearchange to try out to see if it gives the same temporary improvement as I observe...


WOOLY BACKGROUND STUFF:
---------------------------

I've had my E92 330i for about 6 months now, and the poor gearchange through low gears has really put a black cloud over my experiences with my first BMW...

I've been down the whole warranty investigations route, but as it was not from a main dealer, they just sent me off to several "specialists", who each insisted that they had fixed the issue by putting a magical oil in the box.

Well nothing has worked, and I got fed-up with all the messing about.


MY TECHNICAL OPINION:
-----------------------

After considering all the possibilities I could think of that could cause a bad gearshift (baulking, thumping into gear - especially when cold), the fact that the problem decreases in correlation with gear ratio, in my mind I kept going back to clutch drag as the most likely cause.

I had originally discounted the clutch, as when stopped at idle, I can select a gear, and then -> neutral -> re-select same gear, ad you can tell that the input shaft has not moved from where it previously was, as there is much less force required to select the gear the 2nd time around.


I recently tried changing gear and holding the revs up - rather than completely releasing the accelerator, and gearchange seemed to be much smoother.... Well the clutch is open when selecting the next gear, so how could the higher revs be affecting the shift???

I considered that although the clutch was not dragging significantly when engine is at idle, and input shaft is stationary (+ve rotational delta across the clutch plates)... What if the clutch was gripping more when slipping in the opposite direction (e.g when engine revs dip right down upon shifting, but input shaft is spinning faster)?

This doesn't quite add up admittedly, as the input shaft actually wants the slow down anyway on an upshift, but it seems to fit the experimental observations.

THE SIGNIFICANT EXPERIMENT - please give this a go and report:
--------------------------------------------------------------

I considered that perhaps if the clutch surface had been conditioned by use to align in one direction, and grip more in the "slowing the gearbox down" direction, then I could try to rub the surface back the other way...

So I went for a drive and at about 60MPH, I engaged clutch, carefully selected 2nd (pushing the synchros a bit at this speed), and then VERY GENTLY lifted the clutch - JUST A LITTLE - until the engine revs rise up a bit - perhaps to about 2k - so that you can feel a bit of engine braking, but the clutch is still slipping well.

This is really polishing the clutch surface backwards...

I did this for perhaps 5 seconds, sped up again and repeated.

After this, I stopped. Set off again up through the gears, and they all selected like butter - all the nasty awkward changes were GONE!

The "treatment" is relatively short-lived though, and I suspect that if you drive hard, and slip the clutch a lot on upshifts, then it quickly resets this polishing.

For me anyway, it is just a diagnosis that the gearchange issue is likely a clutch problem... Perhaps there could be air in the clutch fluid, and it doesn't disengage entirely? I really haven't gone any further, but wanted to float the idea/observation to see if anyone else with the problem sees the same "clutch polishing" improvement, or if any experts could comment on whether I have lost my mind!!!


Thanks for reading!

James

[xenon]

Could be the crappy CDV.

[M3-FAST]

Originally Posted by xenon

Could be the crappy CDV.

+1 - remove the CDV and all will be fine!

http://www.e90post.com/forums/showthread.php?t=29828

Do a search - there are tons of threads on this.

[doughboy]

James,

I take it you know about CDV's?

Have the CDV (clutch delay valve) replaced for a derestricted one by any decent BMW independant. No one will ever know.

item 13 on here is the offending unit http://www.realoem.com/bmw/showparts...08&hg=21&fg=10

I had it done for £30 fitted at Darren Wood BMW in Stockport and it transforms the gear shift like you WOULD NOT BELIEVE. I had also spent ages analysing the poor shift on the 335i and my previous 330i and could not believe it could have so much effect until I finally got rid of it. Now low speed 1st to 2nd shifts are perfect and without and shunt or passenger head shaking!

You can buy one for about £5 from BMW and pop out the one-way valve assembly yourself leaving it as a straight through pipe.

It can then be easily swapped for the old one and the clutch bled through.

[rogerxp]

+1 what these chaps said.

I never got round to doing it on the 330d but, if I'd have planned keeping it for longer (or if SpeedReligion hadn't shut-up-shop just as I was about to do it), I'd have definately done it. For the price involved it's a no brainer.

Between the CDV and RFT's it's amazing BMW ever managed to sell and E9X's.

[doughboy]

Originally Posted by rogerxp

+1 what these chaps said.

I never got round to doing it on the 330d but, if I'd have planned keeping it for longer (or if SpeedReligion hadn't shut-up-shop just as I was about to do it), I'd have definately done it. For the price involved it's a no brainer.

Between the CDV and RFT's it's amazing BMW ever managed to sell and E9X's.

Should have gone to Darren Wood in Bredbury, £30 and free coffee..

CDV's are on 1, 3, X3, 5 & X5 models too. What are BMW doing?

I think its to protect the manual boxes from ham-footed drivers from a certain continent where they all drive autos....

[JamesUKE92]

Hi Chaps,

Thanks a lot for the quick replies on this... I had indeed read about the CDV, and it's effect on gearchange, and I was under the impression that it could not cause what I'm experiencing, but a different symptom - being less predictable take-up of torque while releasing the clutch (after the actual shift)...

From what I understand, the CDV will allow the clutch to part just as fast as it would without the CDV, but limits the rate that the clutch can re-engage (return of fluid from the slave cylinder).

My symptom is that it is difficult to select the gear that I'm shifting into because of the synchros baulking... Especially in cold weather.

I am prepared (and eager) to be corrected on this, as simply blowing away the CDV would be a really simple job if it could really fix this...

Can you guys confirm whether your "pre-CDV delete" gearshifts were bad due to baulking into gears, or due to jerky engaging of torque when releasing clutch after a shift?

I'd always assumed the latter due to my (possibly incorrect) understanding of the nature of the CDV.

Thanks again
James

[doughboy]

James - my thoughts were the same as yours as i couldn't understand how a restricted clutch engagement could cause all the problems I had.

My issue was with a sticky shift from 1st to 2nd and 2nd to 3rd, even with the clutch pedal on the floor - unless really going for it at higher revs, this was combined with it being very hard to get a good quick take up of drive without jerkiness - again far worse at low speed / revs.

At low speeds you simply couldn't do a quick in-out upshift as you can with other cars.

As soon as I had the CDV removed all these problems went away. the 'box just snicks from 1st to 2nd and 2nd to 3rd wonderfully with immediate jerk-free take up afterwards, I now don't use the full pedal travel to get perfect shifts as you can modulate the clutch so accurately without the CDV - just like any other 'normal' manual.

I thinks it might be more to do with the speed of the shift being so much greater without the CDV that it all just 'works' how it should do.

Don't ask me how - just cough up the £30!

Where abouts are you?

[JamesUKE92]

Thanks Doughboy, I now have renewed hope that I may actually get the problem fixed without selling one of my internal organs!!! >£3k for a gearbox was starting to sound like the only solution!

Sounds like I'll take a punt on the CDV seeing as it's such a cheap option, and see if I get as lucky as you did...

I'm down south by the way... Near Swindon.

It does seem a shame to not fully understand the mechanism of the problem though, and why the CDV bypass would affect it... Could it be that it screws up whatever auto-adjusts the position of the biting point - if there is such a thing?

[doughboy]

Give Birds BMW in Iver a ring - they might tempt you with some other stuff too

[Jamese93]

Originally Posted by JamesUKE92

Hi Chaps,

Thanks a lot for the quick replies on this... I had indeed read about the CDV, and it's effect on gearchange, and I was under the impression that it could not cause what I'm experiencing, but a different symptom - being less predictable take-up of torque while releasing the clutch (after the actual shift)...

From what I understand, the CDV will allow the clutch to part just as fast as it would without the CDV, but limits the rate that the clutch can re-engage (return of fluid from the slave cylinder).

My symptom is that it is difficult to select the gear that I'm shifting into because of the synchros baulking... Especially in cold weather.

I am prepared (and eager) to be corrected on this, as simply blowing away the CDV would be a really simple job if it could really fix this...

Can you guys confirm whether your "pre-CDV delete" gearshifts were bad due to baulking into gears, or due to jerky engaging of torque when releasing clutch after a shift?

I'd always assumed the latter due to my (possibly incorrect) understanding of the nature of the CDV.

Thanks again
James

I don't know if its the same problem I had but...

My e93 had the problem of baulking synchro when cold - went into the garage with the problem and it needed a new box - always did it when cold, particularly changing from first to second at relatively high revs. It didn't do it when warm on test, they kept it overnight, gave it some welly the next morning and tried to change gear and actually succeeded in blowing it up....

Good job the car went back to BMW as a lemon. I'm no expert (I know lots about classics but modern electronics are past my comprehension), but apparently there are electronic dampers within gearbox that can play up, and it sounds like this may be a potential problem?

Good luck!

James

[monkee]

I went to the parts department in my local dealership today (Harry Fairbairn) to enquire about getting a derestricted clutch delay valve. They had no scooby what I was talking about. Does anyone have the part number for it or know where I can get one online?

[doughboy]

Originally Posted by monkee

I went to the parts department in my local dealership today (Harry Fairbairn) to enquire about getting a derestricted clutch delay valve. They had no scooby what I was talking about. Does anyone have the part number for it or know where I can get one online?

No kidding?

If you wanted some illegal drugs would you ask the local police where to get it from?

Or ask the Inland Revenue how to avoid paying tax?

[dxb335d]

Originally Posted by doughboy

No kidding?

If you wanted some illegal drugs would you ask the local police where to get it from?

Or ask the Inland Revenue how to avoid paying tax?

Fackin PMSL.

[monkee]

Originally Posted by doughboy

No kidding?

If you wanted some illegal drugs would you ask the local police where to get it from?

Or ask the Inland Revenue how to avoid paying tax?

I got the impression from this thread it was a part available at the dealership - sooooo sorry...

And thanks for the very helpful response.

[m1bjr]

Originally Posted by monkee

I got the impression from this thread it was a part available at the dealership - sooooo sorry...

And thanks for the very helpful response.

Yes, sad how some assume so much.

These CDVs are fitted in the 04+ S2000 too, I yanked mine out and the difference was massive.
The Hond abox is already one of the best on the market but was marred by the CDV.
An aggresive change was always met with a lot of clutch slip (as designed) but hopeless on a sports car.
Its an easier job on this car, and any competant garage can do the job fairly quickly for you.
You just need the reworked cartridge valve, or take your original out and punch out the end with a 3mm drift and refit/bleed fluid.

S.

[doughboy]

Originally Posted by monkee

I got the impression from this thread it was a part available at the dealership - sooooo sorry...

And thanks for the very helpful response.

Sorry monkee.

Been a long day yesterday, I shouldn't have responded like that, my apologies...


As said, the only the original restricted valve is available from BMW:

Item 13 here gives the part number: http://www.realoem.com/bmw/showparts...08&hg=21&fg=10

You can knock out the internal valve and spring from the assembly with a small drift (many use a 3mm allen key) to make your own derestricted version.

Then this derestricted one can be fitted in place of the restricted one by any competent garage.

You could just derestrict the one you take off the car, but the risk then is that you break it and then you are stuck with no clutch until you can get a new part.

So for the sake of £5 its best to get a new one first IMO.

[willhollin]

So this might stop my wife's head moving backwards and forwards when changing gear?

Most useful.

[doughboy]

That's exactly what happened to me.

No more nodding wife.

[JamesUKE92]

Right, just ordered a new valve from BMW... Will punch out and fit - hopefully at the weekend.

I'm still highly sceptical that it will have any affect on the specific problem I'm seeing, but I'm sure I'll see other improvements at least, so I reckon it's worth doing.

So in addition to doughboy, did anyone else have the same symptoms as me (baulking, not jerking)? Did the CDV delete fix it? If you still have the problem, does my clutch slipping experiment have any effect?

Cheers,
James

[monkee]

No worries - thanks for the info.

Originally Posted by doughboy

Sorry monkee.

Been a long day yesterday, I shouldn't have responded like that, my apologies...


As said, the only the original restricted valve is available from BMW:

Item 13 here gives the part number: http://www.realoem.com/bmw/showparts...08&hg=21&fg=10

You can knock out the internal valve and spring from the assembly with a small drift (many use a 3mm allen key) to make your own derestricted version.

Then this derestricted one can be fitted in place of the restricted one by any competent garage.

You could just derestrict the one you take off the car, but the risk then is that you break it and then you are stuck with no clutch until you can get a new part.

So for the sake of £5 its best to get a new one first IMO.

[mobileadam]

Sounds very interesting. Let us know how you get on James - I might add to the list of jobs I need my friendly mechanic friend to do!