Fitting the CDV back in?

[lightning]

So after reading loads of "remove the CDV for a better gear change" advice, l removed it from my Z3 3.0.

And yes, when shifting quickly at high RPM the clutch no longer slipped for a second. But it was almost impossible to get smooth changes from first to second, under "normal" driving. And to a lesser extent second to third. There was always a lurch as the clutch took up the drive.

So l refitted the CDV, and now it's smooth once again. I just have to remember to take a second during high speed gear changes, to let the clutch engage.

I also imagine that having the CDV is kinder to the transmission, in particular the differential mountings.
Most of the time these parts are fitted for a reason, and try as l might l could not get smooth (as in jerk free) gear changes from first to second without it. Sometimes l managed it, but other times it showed me up.

[Gazza]

try as l might l could not get smooth (as in jerk free) gear changes from first to second without it. Sometimes l managed it, but other times it showed me up.

I had my CDV removed years ago, it may take you a while to get used to it, your quote above suggests as much

[lightning]

Yes l am not sure whether to leave it in or out at the moment.

I can fit/remove it in twenty minutes. The longest part of the job is getting the ramps and extensions out of the shed and getting the car on them.

[Mike Fishwick]

Well, how do you imagine peole in pre-CDV cars manage to change gear? It's just a matter of getting used to your car's characteristics.

[lightning]

I know, but l tried and tried. It should not be that hard. Yesterday l drove a 110,000 mile Transit, a Defender, a 2012 VW Polo, a Transit Connect, and a Suzuki SX4.

I had no problems in any of these vehicles. I think maybe the clutch is defective in my Z3, as in not progressive enough. Because l just cannot get it right.

[pingu]

If you can get a Defender to go into 1st whilst moving at >10mph, you should be able to manage without a CDV.

Have you tried rev-matching? You don't have to get it spot-on (unless your clutch has completely failed).

[edited as "stop-on" makes no sense ]

[Mike Fishwick]

There is o reason why you should have a jerky clutch action, so it is a matter of looking for the cause.

Apart from the clutch itself, the rubber driveshaft coupling may be worth looking at.

[gIzzE]

And what transmission fluid have you got n there? Still got that diff treacle in the 'box?

[lightning]

I did not change the gearbox oil again yet.
The actual gear selection is perfect. It is just matching the RPM when changing from first to second gear.
With the CDV refitted it is much easier. I will have another go at it when l get the chance.

Where is the rubber driveshaft coupling, at the inner or outer end of the drive shaft. Can l check that myself? I take it there are two.

[Mike Fishwick]

By 'driveshaft' I was referring to what is often called a 'propeller shaft' - a curious name for something which does not drive a propeller!

Look at the back of the gearbox, and you will see it - although it should be OK, look for signs of splitting.

[HBmw3]

Wondering, did anybody try this?:

http://www.zeckhausen.com/cdv.htm

If so, what are the experiences?

[gIzzE]

I think on most Zs you can just remove the CDV and atach the pipe direct, if it even has one, many don't.

[HBmw3]

If I am correct only 2.2 en 3.0 have one.
I know you can remove it. But I am curious if anyone has tried the adjusted replacement from Zeckhausen.

[gIzzE]

I am not sure what they offer though?

If you can just bypass the cdv on Z's why do you need it?

Also, it is really simple to remove your current one, pop the grommet out yourself and put it back in again.

[lightning]

On my 2002 3.0 the CDV can be removed and the pipes joined up, so you don't need any parts.

The actual valve on my car is just a brass fitting with a small hole in the middle, to restrict fluid flow. I guess you could drill it out yourself, but why bother putting it back in if you don't want it?
Just join up the two pipes, it takes about five minutes.


http://www.bmwland.co.uk/forums/viewtop ... 7&t=107462

[gIzzE]

I think that site makes more sense if your car is still in warranty, it keeps it looking stock, but when out of warranty just bypass the CDV completely.

[lightning]

Well.....

I took out the CDV again, and have been practising smoother gear changes. I think l am getting the hang of it! The engine is a big lump so needs the revs balancing on gear changing. Plus when you back off the gas the revs drop quickly, unlike some new cars, so it takes time to get used to.

[Rafolian]

Propeller shaft, not really that curious a name for something that is used to "propel" the vehicle forwards or backwards.