Gear shift quality

UK forum for general and technical discussion about the Z3 roadster
Post Reply
User avatar
lightning
Joined: Tue 27 Nov, 2007 08:15
Posts: 818

  Z3 roadster 3.0i
Location: Stockport

Gear shift quality

Post by lightning »

I can't always get a smooth shift from first to second gear on my 3.0 Z3.

Sometimes it is OK but other times it's as if the clutch is dragging, as it clunks into second gear.
I had this same thing on my MX5. The clutch was replaced twice under warranty but it was no better.

It works better if you make sure the clutch is fully down before moving the gear lever. And it never has a problem going into gear when stationary, including reverse.

The thing is, 80% of the time it's fine. Just like the MX5. I don't want to get the clutch replaced if it's not that. I sometimes wonder if l need to change my gear shifting technique.
User avatar
Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Gear shift quality

Post by Southernboy »

Have a look at the slave cylinder clutch hose. They come as completely rubber in OEM form... They also have a restrictive valve in them which adds to the lack of clutch response. If you replace that with a steel braided hose you benefit from less rubber hose expansion under pressure, but you elliminate the valve through which the clutch fluid must pass.... It may be a simple remedy to the gear change difficulty... especially since you mention the clutch needs to be fully depressed at the foot pedal.
"Normal is overrated"
Image

Z3 Upgrades and Additions
gIzzE
Joined: Mon 06 Aug, 2007 21:32
Posts: 169

  Not specified

Re: Gear shift quality

Post by gIzzE »

How long have you had your car?

You said you have changed the gearbox fluid in another thread, but you have now put a differential oil in there that is over twice as thick as the thickest recommend stuff.

When you look at the different viscosities of the recommend oils they vary by around 10-20% between the thinnest and the thickest, you have just put stuff in there that is over twice as thick.

My car used to be really notchy between 1st and second and try and find 5th when going into third, which is why I swapped for a very thin Automatic Transmission Fluid, the Redline D4. This sorted it out completely.
Before swapping clutches I would get the correct fluid into your gearbox.

As said above though, well worth removing the clutch delay valve, it is there to put less strain in the clutch, but ruins the feel of it.
User avatar
lightning
Joined: Tue 27 Nov, 2007 08:15
Posts: 818

  Z3 roadster 3.0i
Location: Stockport

Re: Gear shift quality

Post by lightning »

Yes the clutch does have an odd, almost "remote" feel.

The gearbox oil l used was SAE 75w/90 and the recommended oil for my car is SAE 75w. So it is not twice as thick, but will indeed be thicker at higher temperatures.

Changing the gearbox oil improved the shift quality a lot. But it did not stop this intermittent issue. I am going to change the gearbox oil again anyway, and l will also take the advice above and replace the slave cylinder hose. Can somebody point me in the direction of a suitable repacement for the original hose?
As l assume it's not a BMW part.
User avatar
Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Gear shift quality

Post by Southernboy »

Do a search in the Z3 posts... many write-ups and as many sources... try search under "braided clutch hose"... should turn up lots.. :wink:
"Normal is overrated"
Image

Z3 Upgrades and Additions
gIzzE
Joined: Mon 06 Aug, 2007 21:32
Posts: 169

  Not specified

Re: Gear shift quality

Post by gIzzE »

It is actually more than twice as thick, over twice as thick at 100ºc and over 3x as thick at 40ºc.


This is what you have put in....

Viscosity @ 40º C 103.7
Viscosity @ 100º C 15.7

Compare that to my ATF D4.....

Redline D4 ATF
Kv @ 40c = 34
Kv @ 100c = 7.5



The following are recommended oils for a slick change for comparison...

Pentosin MTF-LT-2

Kv @ 40c = 38.3
Kv @ 100c = 7.7

Amsoil Universal ATF (New Formula)

Kv @ 40c = 38.5
Kv @ 100c = 7.5

Redline D4 ATF
Kv @ 40c = 34
Kv @ 100c = 7.5

Royal Purple Synchromax
Kv @ 40c = 38
KV @ 100c = 7.7

Royal Purple ATF
Kv @ 40c = 35
Kv @ 100c = 7.5


So you can see how far out the specs are for the oil you have in there. And what is it like at 5ºc? It may be like treacle.

The 75w90 vs 70w80 vs 75w means very little, same as you can get a 10w40 that is thinner than 0w30 at the given spec temps.

With a really thick diff oil in your gearbox you can't really tell what is going on with gear changes, until you get the right oil in there don't start throwing money at other stuff.
User avatar
c_w
Joined: Thu 19 Aug, 2004 16:50
Posts: 4032

  M roadster S50

Re: Gear shift quality

Post by c_w »

It's the nature of the gearbox, you won't ever cure it. Sometimes mine is notchy other times it's really smooth.

New gearbox oil is your best bet to better the shift quality.
gIzzE
Joined: Mon 06 Aug, 2007 21:32
Posts: 169

  Not specified

Re: Gear shift quality

Post by gIzzE »

Totally agree, I have been on various BMW forums for the last 17 years, covering E36s, E46s, E39s, E60s, E90s etc. etc. and 1st to 2nd gear shift is one of the most discussed issues.
And always improved with a less viscous oil in there.
User avatar
lightning
Joined: Tue 27 Nov, 2007 08:15
Posts: 818

  Z3 roadster 3.0i
Location: Stockport

Re: Gear shift quality

Post by lightning »

Ah well, out comes the £40 worth of Castrol 75w/90 then....maybe l will put it in my van gearbox instead
gIzzE
Joined: Mon 06 Aug, 2007 21:32
Posts: 169

  Not specified

Re: Gear shift quality

Post by gIzzE »

Haha, put it in the diff if you haven't done that yet.

Is it rated for Limited Slip Diffs?
User avatar
lightning
Joined: Tue 27 Nov, 2007 08:15
Posts: 818

  Z3 roadster 3.0i
Location: Stockport

Re: Gear shift quality

Post by lightning »

That's a whole other subject lol

Should l start a thread on it? There hasn't been a "what oil for my differential" for a while :-)
gIzzE
Joined: Mon 06 Aug, 2007 21:32
Posts: 169

  Not specified

Re: Gear shift quality

Post by gIzzE »

Haha. :D


It's not listed as suitable for a limited slip diff. unfortunately.
Gareth 161
Joined: Thu 08 Mar, 2012 23:41
Posts: 137

  Z3 roadster 3.0i
Location: Cornwall

Re: Gear shift quality

Post by Gareth 161 »

I had the same notchy/difficult gear change from 1st to 2nd and changed the gearbox oil and put a braided hose on which has improved it dramatically.
Unfortunately therefore not sure which made the most difference as both done the same time but as the oil which came out did not look too bad, perhaps it was the hose. I know when I looked at the old hose when applying the clutch pedal(well someone else pressed the pedal), you could see/feel it bulge.
However as both are reasonably cheap fixes, I was just happy to do both at the same time to sort the problem.
Hope this helps.
Gareth
2001 3.0 Z3, 2008 Subaru Forester Xten
User avatar
lightning
Joined: Tue 27 Nov, 2007 08:15
Posts: 818

  Z3 roadster 3.0i
Location: Stockport

Re: Gear shift quality

Post by lightning »

Alright....

I dropped out the Castrol Syntrax 75w/90 and refilled with Castrol Syntrans B75w

Let's see if the gear change is any better!
User avatar
lightning
Joined: Tue 27 Nov, 2007 08:15
Posts: 818

  Z3 roadster 3.0i
Location: Stockport

Re: Gear shift quality

Post by lightning »

So, after 300 miles of driving this weekend, l can report that it IS better with this lighter oil in it.
Post Reply