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      07-22-2010, 09:49 PM   #155
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Yes, lonestar bravarian, I was talking to Trent. It was not at a track but at mineral wells for an autocross event with the BMW group. The backside was faster requiring 3 rd gear then with an increasing slalom at the end on deceleration before a hard left. I tried to shift to 2nd before the hard turn but I was always denied.
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      07-24-2010, 02:39 PM   #156
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Quote:
Originally Posted by jragan View Post
I'm going to be the a-hole and come out and say that your bushings aren't going to "solve" this....The problem is in the synchros and the speed at which they engage (which is why a fraction of a fraction of a second of added pause with the clutch in or slipping the clutch the tinyest bit solves the problem). After you install the bushings, once you relax and settle back into your driving habits, you'll start grinding again.
It looks like you were proven right regarding "the grind". Blind32 installed super-stiff mounts, and the grind is still there.

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Originally Posted by Blind32 View Post
Thanks all.

Well, 2 grinds yesterday I've put about 150 miles on the car....

Both times I grinded, I was doing everything correctly. I now believe this issue is just something to do with the high rpm and the tranny. I don't know anything about the inner workings of transmissions so I won't even begin to guess.
As inTgr8r put it in one post....

There are three separate issues:

a) 1-2 grind which is tranny design/synchos; other fluid may help RP Synchromax, Redline MTL etc.
b) Downshift to 2nd gear rejection under loading conditions. = tranny mounts
c) Clutch engagement feel = CDV

Given the input of other drivers and some indie shops, I think the tranny mounts will help with issue "b", but I guess we won't have definitive data on that until someone who has had issues tests the new mounts under the same conditions.

Given that we've ruled out things we can easily modify (CDV, mounts, shifters) I think this points to an internal design flaw--or more likely a design deficiency (they didn't build a transmission spec'd to this motor). I've read, or think I've read, that the transmission in the Z4M is actually from the regular Z4. If that's the case, it may have never really been designed to handle the higher-revs the Z4M throws at it. The two times I've had "grind" were shifting at high RPMs--and that's where maximum torque with this engine lives as well. Even in the 4K+ range the Z4M motor kicks out a lot more power, and the tranny has to deal with that. It may not be up to the task....and there's going to be no cure for that (even a replacement transmission won't solve it).

My solution, for now, for the 1st-2nd issue is to shift earlier into 2nd. Not ideal, but I don't really see this as a drag-racing car, and the only other place it could present an issue is launching in autox. And I can't recreate it easily--it's happened very rarely.

BMW transmissions are beginning to annoy me a bit. There are the Z4M issues, and I've had my fair share of software issues with my DCT. I really love our cars, but damn, I have an 95 Integra with 170K miles (a bit "worn" with minimal maintenance levels over its life) and you can rev that baby under WOT to the 8K redline all day 1st to 2nd, downshift 3rd to 2nd at high revs and load, and it shifts like a dream. For the price, we really should not be dealing with pissy little problems like this with top tier vehicles like the Z4M.

Last edited by Finnegan; 07-24-2010 at 02:47 PM..
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      07-26-2010, 01:57 PM   #157
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Quote:
Originally Posted by Finnegan View Post
For the price, we really should not be dealing with pissy little problems like this with top tier vehicles like the Z4M.

+1. I really love my car, but I think the z4m and its coupe variant were afterthoughts.
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      07-26-2010, 03:04 PM   #158
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^^^ not everyone has the grind, maybe there are some defective transmissions out there? I've found all BMW trannys to be notchy, and come to expect that as they seem to last a very long time. It would be nice to see who has the most mileage and how the tranny has 1. held up and 2. if it smoothed out over time
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      07-26-2010, 03:34 PM   #159
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thekurgan, mine's a 2006, UK, right hand drive car with about 34-35,000 miles on it and it grinds.
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      07-26-2010, 03:37 PM   #160
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I'd like to suggest that everyone who has the grind moves their seat forward by 1" (~2.5 centimeters) and reports back with how this has affected their grinding.
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      07-26-2010, 03:40 PM   #161
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Quote:
Originally Posted by jragan View Post
I'd like to suggest that everyone who has the grind moves their seat forward by 1" (~2.5 centimeters) and reports back with how this has affected their grinding.
Well it's already pretty far forward. When i fully press the clutch for example my knee is still bent a bit...
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      07-26-2010, 03:48 PM   #162
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Quote:
Originally Posted by jragan View Post
I'd like to suggest that everyone who has the grind moves their seat forward by 1" (~2.5 centimeters) and reports back with how this has affected their grinding.
Are you suggesting that we're not pushing the clutch far enough (because we're too far back), that our arms are reaching too far ahead (because we're too far back), that it's general driver's error, or something else?
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      07-26-2010, 03:52 PM   #163
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Quote:
Originally Posted by ga41 View Post
thekurgan, mine's a 2006, UK, right hand drive car with about 34-35,000 miles on it and it grinds.
35k miles? she's still a baby, I mean like 100k+
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      07-26-2010, 04:07 PM   #164
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Mine only has 22K (who knows what the previous owner did the first 20k though) and it grinds and rejects shifts. I don't think it's going to get any better with age / use.
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      07-26-2010, 04:18 PM   #165
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Anyone else moved to MTL or a MTL - MT-90 50/50? I'm curious to this result, if not for the grinding, but if anyone else has noticed a smoothness in the heat.
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      07-26-2010, 04:57 PM   #166
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Quote:
Originally Posted by esqu1re View Post
Are you suggesting that we're not pushing the clutch far enough (because we're too far back), that our arms are reaching too far ahead (because we're too far back), that it's general driver's error, or something else?
If I told you what I thought the problem is, it would sway the test results
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      07-26-2010, 06:38 PM   #167
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Quote:
Originally Posted by thekurgan View Post
Anyone else moved to MTL or a MTL - MT-90 50/50? I'm curious to this result, if not for the grinding, but if anyone else has noticed a smoothness in the heat.
I will be changing this week.
I won't be on the track again though for a month. (vacation)
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      07-26-2010, 06:43 PM   #168
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Quote:
Originally Posted by inTgr8r View Post
I will be changing this week.
I won't be on the track again though for a month. (vacation)
Nice, let us know what you think.
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      07-26-2010, 07:12 PM   #169
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Quote:
Originally Posted by jragan View Post
I'd like to suggest that everyone who has the grind moves their seat forward by 1" (~2.5 centimeters) and reports back with how this has affected their grinding.
Wouldn't we want to also include data on whether "frequent grinders" have a modified clutch stop?
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      07-26-2010, 10:30 PM   #170
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Quote:
Originally Posted by Finnegan View Post
Wouldn't we want to also include data on whether "frequent grinders" have a modified clutch stop?
In some cases, after market clutch stops have actually exacerbated the problem (which has led me to ponder whether the actual problem may be that the clutch pedal, from the factory, is adjusted too shallowly)
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Last edited by jragan; 07-27-2010 at 12:01 AM.. Reason: clarified
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      07-26-2010, 10:58 PM   #171
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I have no idea how to adjust a hydraulic clutch...is it adjustable? Years ago I'd adjust the old cable stow clutches myself, but this one?
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      07-27-2010, 12:02 AM   #172
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I have no idea how to adjust a hydraulic clutch...is it adjustable? Years ago I'd adjust the old cable stow clutches myself, but this one?
Sorry, I meant the clutch pedal travel, not the actual clutch hydraulic system. That being said, I've no idea if ours is adjustable.
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      07-27-2010, 06:49 AM   #173
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What's interesting is that I felt like when I test drove an Imola Red M roadster earlier this year, it felt like the clutch travel was noticeably shorter than on the Z4 3.0si coupe I was driving at the time, which contributed to the sportier and faster impression (M power aside). It was a CPO so I think it should have been stock, but I admit I didn't check to see if there was an aftermarket clutch stop. I don't know if I've just gotten used to the shorter clutch travel, but it seems like on the Z4 M I'm driving now, it wasn't short as the one I test drove.
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      07-27-2010, 09:05 AM   #174
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Quote:
Originally Posted by dekaliber View Post
What's interesting is that I felt like when I test drove an Imola Red M roadster earlier this year, it felt like the clutch travel was noticeably shorter than on the Z4 3.0si coupe I was driving at the time, which contributed to the sportier and faster impression (M power aside). It was a CPO so I think it should have been stock, but I admit I didn't check to see if there was an aftermarket clutch stop. I don't know if I've just gotten used to the shorter clutch travel, but it seems like on the Z4 M I'm driving now, it wasn't short as the one I test drove.
The tranny is the same as the 3.0si, but not the clutch. M model uses the heavy duty clutch, which I thought had longer travel. I have heard of some E85/86 M owners with aftermarket clutches and flywheels but never thought to ask about these issues with the notchiness and 1->2 issues.
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      07-28-2010, 02:22 PM   #175
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i never have a grind into 2nd but i do get rejected sometimes during very aggressive driving from 1st into 2nd. im trying to pinpoint when this happens, but im not quite sure. i might do the CDV delete and see if that helps.
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      07-28-2010, 03:01 PM   #176
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i never have a grind into 2nd but i do get rejected sometimes during very aggressive driving from 1st into 2nd. im trying to pinpoint when this happens, but im not quite sure. i might do the CDV delete and see if that helps.
CDV won't help that situation, it is only when the clutch engages, the valve is a one-way valve.
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